GLOSSARY

A comprehensive glossary of watchmaking and watch culture terms

- T Swiss Made T -	A marking that (probably) indicates that the wristwatch’s total tritium emits less than 7.5 millicuries. In the context of Rolex watches, there is an understanding that it also indicates that the indices are made of gold, which is likely not entirely true due to several references having both steel indices and this marking. This marking is often compared to its contemporaries, namely ‘T Swiss T’ and ‘T Swiss Made T’. The exact differences are poorly understood, with conflicting information from various sources and no official statement from Rolex. The tentative consensus seems to be that the variation is a result of a lack of standardization, which is a common theme in Rolex watches before the 1990s.
/ (reference number)	In reference numbering convention, a slash symbol is used for two purposes. First, it can be used to list several similar reference numbers (which usually indicate similarity in design or movement) efficiently. For example, Seiko references 6306 and 6309 are almost the same watch and have almost the same reference. Thus they can represented as 6306/9. How many digits one places behind the slash is entirely up to how self-evident it needs to be, at the expense of brevity. When referring to a large family of such references, an 'X' is often used to represent the variable digits. See 'X (reference number)'. The second use of the slash is as a divider to accentuate or add a piece of information. For example, the 0 in Tudor ref.7016/0 indicates that that particular watch was made in steel. Hence, in the case of (vintage) Tudor, ref.7016/0 is not two references but one.
12-hour Clock	A time convention in which the 24 hours of the day is divided into two halves, the first half from midnight (12:00 a.m.) to noon/midday (12:00 p.m.) denoted ‘a.m.’ and the second half from noon/midday to midnight denoted ‘p.m.’.
12-hour Dial	A dial that uses 12-hour notation. It must be combined with a 12-hour hand. This is the most common configuration for an analog watch.
12-hour Hand	A hand that makes a full lap around the dial every 12 hours. It is the standard hour hand.
12-hour Notation	A notation of timekeeping that indicates the time of day from 12:00 a.m. to 11:59 p.m., based on the 12-hour clock.
120-click Bezel	A click bezel with 120 positions. The positions align with each hash on the minute track and the space in between.
12SA	12 Saphirs. Rolex nomenclature for a bezel set with four sapphires at the hours interspersed with forty-eight diamonds.
24-hour Clock	A time convention in which the 24 hours of the day starts at 00:00 and ends at 23:59. The 24-hour clock has superior clarity to the 12-hour clock and is used in applications that require brevity and clarity such as hospitals and the military. Hence, it is also commonly called ‘military time’, although there are differences.
24-hour Dial	A dial that uses 24-hour notation. It must be combined with a 24-hour hand.
24-hour Hand	A hand that makes a full lap around the dial every 24 hours. This hand is usually used as GMT hand to indicate a second timezone. However, it may also serve as the regular hour hand for a watch with a 24-hour dial.
24-hour Notation	A notation of timekeeping that indicates the time of day from 00:00 to 23:59, based on the 24-hour clock.
316L	A type of stainless steel very commonly used in the watchmaking industry. Like all stainless steels, 316L is composed primarily of iron, with copious amounts of chromium, nickel, and a small amount of molybdenum and other elements like silicon. The L in 316L signifies that it is a low carbon variant of 316. The lion's share of watch manufacturers use 316L. Manufacturers with more flowery marketing refer to 316L as 'surgical grade steel'. 316L is in fact used widely in the medical industry and maritime industry.
4RU	4 Rubis. Rolex nomenclature for a bezel set with four rubies at the quarters interspersed with thirty-six diamonds.
60% Rule	An often pejorative term denoting the ordinances on Swiss origin markings. The term emphasizes that only 60% of costs need be incurred in Switzerland for a watch to be officially 'Swiss', meaning that close to half of the costs may go towards imported components. It is often used to make the point that 'Swiss made' is not a meaningful sign of quality or Swissness.
60-click Bezel	A click bezel with 60 positions. The positions align with each hash on the minute track.
904L	A type of stainless steel commonly used in the watchmaking industry. Like all stainless steels, 904L is composed primarily of iron, followed by chromium, nickel, molybdenum, and other elements. 904L has a particularly high amount of chromium which gives it a much higher resistance against corrosion and pitting. Despite its being softer than the industry standard 316L, its softness allows it to be polished to a higher degree and its corrosion resistance retains its original luster for longer. For these reasons 904L is used by Rolex.
A. Lange & Söhne	A watch manufacturer established in Glashütte, Germany in 1845 and revived from communist nationalization in 1990. Abbreviated ‘ALS’ and alternatively written ‘A. Lange & Soehne’ to render the umlaut in the English alphabet. A. Lange & Söhne is owned by Richemont.
a.m.	(Latin) Ante meridiem. The first twelve hours of the day in a 12-hour clock. Starts at 12 a.m. (midnight) and ends at 11:59 a.m.
Ab	(German) 'Down'. Empty.
ABC	‘Altimeter, Barometer, Compass’. A name for three major functions that are useful for land activities. An ABC-capable watch allows its wearer to understand his/her bearings, elevation, and forecast the weather. Typically a watch that has all three functions are digital quartz watches purpose-built for exploration or combat.
aBlogtoWatch	An online watch publication based out of Los Angeles, USA.
Abraham-Louis Breguet	(1747-1823) A horologist from Neuchâtel, Prussia and active in Paris, France. Breguet is credited with inventing the gong spring, flat balance spring with overcoil, the first execution of the tourbillon, and countless other aesthetic innovations and technical improvements that heavily impacted the course of timekeeping and horology.
Accuracy	A measurement of the difference between time kept by a timepiece and real time. The latter is usually represented by the most accurate timepiece available, which in our age would be atomic clocks. In the most practical sense accuracy simply refers to the consistency of the timekeeping component such as the oscillations of a balance or vibrations of a quartz crystal. Accuracy is measured by number of seconds deviated (in positive or negative notation) over a certain period of time. The most common is [+/- n seconds per day].
Acrylic/Plastic	A thermoplastic also known as poly(methyl methacrylate). It is also known by its many commercial names like plexiglas, acrylite, perspex, and hesalite. It rates a 3 on the Mohs hardness scale. Acrylic crystals are common in vintage watches. While some think acrylic is inferior to mineral and sapphire because of its softness, acrylic is loved by many for how it interacts with light, its warmth, and variety of shapes. Acrylic also possesses many practical advantages. It is highly break-resistant and impact-resistant, and does not shatter. The small scratches and dents it picks up due to its softness can usually be buffed out easily.
Adjustment Hole	A hole in a strap for a pin/tang/ardillon. A strap will usually have six or more of such holes to accommodate different wrist sizes as well as periodic changes in wrist size due to temperature.
Admiralty	A nickname for models of the Omega Genève which feature an anchor at the six o’clock position.
Aftermarket	A component that is not manufactured by the original manufacturer. Antonymous with ‘factory’. The term is usually used for easily-replaceable parts that are commonly offered by third-party makers such as crystals, bezels, bracelets, and straps. It is also commonly used to describe diamond settings as aftermarket diamonds command a much lower price than factory diamonds.
Agnelli	A byword for wearing a wristwatch over a cuff. Named after Gianni Agnelli, Italian industrialist and senator who was famous for wearing his watches over the cuff. See 'watch over cuff'.
Aiguilles à Pomme	(French) Apple hands. Invented by Breguet’s master Jean-Antoine Lépine, they were the original ringed hands that influenced the Breguet hands.
Alarm	A striking complication that sets off an alarm at a designated time. Most alarms work by releasing spring-stored power into a hammer which strikes a membrane. The alarm will run for either a preset time or until power runs out. Many alarms possess a secondary spring solely for the alarm complication instead of drawing power from the mainspring.
Albatross	A nickname for the Omega Chrono-Quartz reference ST396.0839. The name comes from the shape of the cal.1611’s twin battery contacts (the metal holders that retain the coin batteries) resemble a bird with outstretched wings. The same watch is also called the ‘Montreal’ and the ‘Olympic’.
Albino	A nickname for a white variant of a normally other-colored dial. Famous Albinos include the Rolex Explorer I ref.6610 Albino and the Omega Speedmaster Professional ref.3593.20.00 Albino.
Alignment	The alignment of the different components of the dial to each other. When alignment is poor, the hour markers may not be aligned with the minute track or the dial itself may be askew.
All-or-nothing Mechanism	A mechanism in a striking movement which disarms or blocks the cadrature if there is not sufficient power reserve to sound the next chime. It is usually in the form of a spring lever which obstructs the repeater works until the slide is fully pulled. All-or-nothing mechanisms prevent the watch from being misunderstood by the wearer in case the chime is cut off by insufficient power.
Alpha Hands	A style of hands distinguished by a rapid taper from a skinny base to the shoulder and a gradual taper from the shoulder to the tip. An alpha hand resembles a spearhead where the base resembles the socket, the shoulder the transition, and the rest of the hand the blade. For this reason they are also called ‘lance hands’. Alpha hands may be lumed or unlumed.
Alpha/Alfa Timezone	Military timezone name for UTC-1.
Altimeter	An instrument that measures altitude. Altimeters can be useful for land exploration, especially for mountaineering.
Amplitude	The rotation angle of a single semi-oscillation of the balance. The balance wheel attached to the balance spring spins in an incomplete circle in one direction and then swings back in the other direction. Each spin is called a semi-oscillation, which also constitutes a single beat for the movement as each spin provides an input to the escapement. The amplitude of a movement is how far, in degrees, the balance wheel swings. Amplitude is often correlated to the health of the movement and should be neither excessive or insufficient.
Ana-digi	Analog-digital. A watch that has both analog and digital displays. While many mechanical watches that have a digital display also have an analog display (usually for the seconds which can be difficult to engineer digitally in a mechanical movement), this term mostly applies to quartz watches with an LCD (sometimes LED) and an analog handset. This does not count if the hands are displayed on an LCD screen.
Anakin Skywalker	A nickname for the Omega Seamaster reference 145.023, a tungsten-cased chronograph with a colorful dial. The name is a reference to the popular science fiction franchise Star Wars. The nickname ‘Anakin Skywalker’ was dubbed by renowned collector Chuck Maddox as it was the appropriate name for the original, non-PVD version of the black 145.0023 ‘Darth Vader’. In Star Wars lore, Darth Vader is the name of Anakin Skywalker after he turned to the Dark Side much like how the ref.145.0023 and the ref.145.023 are essentially the same watch but in opposite colors.
Analog Display	A display which uses hands to tell the time. Antonymous with 'digital display'.
Analog Watch	A watch with an analog display. Antonymous with 'digital watch'.
Anchor Escapement	An escapement for pendulum clocks that utilizes the swinging motion of the pendulum to lock and unlock the escape wheel. The 'anchor' is a component shaped like an upside-down boat anchor. The shank (shaft) of the anchor is connected to the swinging pendulum while the arms of the anchor each has a claw called a pallet. The swinging motion of the pendulum makes the pallets catch and release the sloped teeth of the escape wheel. With this mechanism, the speed of the pendulum controls how fast the escape wheel turns. A simple but highly effective mechanism, the anchor escapement is common in pendulum clocks.
Anchor Governor	A governor for a striking train which employs an anchor escapement to regulate the strike tempo. The pallets on the anchor lock and release the escape wheel which controls the unwinding speed of the repeater mainspring.
Ancre	(French) ‘Anchor’. Although it can refer to any anchor-shaped component, it almost always refers to the pallet fork. See ‘pallet fork’.
Angbuilgu	(Korean) A hemispherical sundial designed in 15th century Korea as an affordable and mass-producible alternative to the more sophisticated striking clepsydras of the era. Angbuilgus were cast in bronze and varnished black with inlaid silver for the markings. They were capable of telling the time as well as the seasons and 24 solar terms.
Anglage	(French) Chamfering.
Angled Lugs	See ‘faceted lugs’.
Annual Calendar	A calendar complication that accurately represents the lengths of all months except February. In terms of ability it is between a simple calendar which must be manually adjusted five times every year and a perpetual calendar which must be adjusted three times every four centuries. Annual calendars provide most of the functionality of a perpetual calendar at a much lower cost and simpler, more reliable engineering, which makes them a popular choice.
Anonymous	A designation for a timepiece with an unsigned dial and unknown brand. Anonymous dials overlap somewhat with sterile dials, but the terms differ in usage. Anonymous dials must be unsigned with no information of the original manufacturer or brand - hence, they are sterile dials with an unclear origin. As anonymous watches usually still have signed movements, they are often called by their movement makers. E.g. ‘anonymous chronograph with Valjoux 22’ or ‘anonymous Valjoux 22 chronograph’.
Aperture	A cutout in the dial which reveals what is underneath. Synonymous with 'window', although the term 'aperture' is slightly broader. Apertures can reveal a disc which displays the date, day, or simply expose a part of the movement.
APH Dial	A nickname for certain examples of the 11652X series Rolex Oyster Perpetual Cosmograph Daytonas with a minute font spacing error. This error makes ‘Cosmograph’ look like ‘COSMOGR APH’, hence the name ‘APH’.
Applied	A component is applied when it is finished separately and attached to the dial surface. It may also be called 'raised' or 'appliqué'.
Arabic Numerals	A type of numerals commonly featured on watch dials, also called Hindu-Arabic numerals or Ghūbar numerals. Arabic numerals are the most widely used number symbols in the world and are commonly found on watch dials, especially those made for high legibility. Not to be confused with 'eastern Arabic numerals'. Sometimes Arabic numerals are called 'western Arabic numerals' to intentionally distinguish them from their eastern counterparts.
Arbor	An axle or shaft on which gears such as wheels and pinions are mounted. The term also refers to the axle of a mainspring barrel to which an end of the mainspring is attached.
Archives	Short for ‘extract from the archives’.
Ardillon	See 'pin'.
Ardillon Buckle	See 'pin buckle'.
Arnie	A nickname for the Seiko reference H558 ana-digi quartz diver as well as the modern SNJ02X series watches inspired by it. The name comes from bodybuilder, actor, and former governor of California Arnold Schwarzenegger, who wore the watch in the 1987 film Predator.
Arrow Hands	A style of hands distinguished by an arrow tip. The body of an arrow hand is usually tapered from a wide base to a thin neck. Arrow hands may be lumed or unlumed.
Art Deco	A style of visual arts, industrial design, and architecture that dominated much of the United States and Europe in the interwar period, particularly during the economic and cultural height that was the Roaring Twenties. Art Deco is an eclectic style that combines a bold and geometric aesthetic language, stylized forms of nature such as foliage and sun rays, and liberally interpreted artistic styles from ancient Egypt, India, China, and Mesoamerica. In essence, Art Deco was an international style that permeated the northern Atlantic and symbolized the West's modern technology, boundless wealth and opulence, resplendent cultural maturity and experimentation, and cosmopolitan trade. In watchmaking, Art Deco had a monumental impact on the design of watches, birthing entire categories of watches like cocktail watches as well as numerous iconic models, numeral fonts, and case designs adored today.
Articulating Lugs	Lugs which pivot on an axis. Articulating lugs can come in many styles. They are helpful in making larger watches more wearable on smaller wrists.
Ashtray	A nickname for the Seiko references 7C46-6009 and 7C46-6010 which have deeply scalloped bezels which somewhat resemble an ashtray.
Asthmometer	A scale that measures respirations. The asthmometer uses the basic formula of a tachymeter which measures frequency over a second-defined period. Because its purpose is more specific, the asthmometer specifies how many respirations it is graduated for. If it says five, the wearer will count five respirations immediately after starting the chronograph. The number the seconds hand indicates at the end of the fifth respiration is rate of respirations per minute. Asthmometers are frequently found in medical watches, and almost always accompany pulsometers. They must be accompanied by some sort of chronograph that allows the wearer to start, stop, and reset the seconds hand at will.
Astronomical Complications	A family of complications that concern the movement of astronomical objects. While some may classify calendar complications as a subgroup of astronomical complications because our calendars are based on the movements of the Earth, Sun, and Moon, in common usage astronomical complications focus more on celestial activities that do not affect our common calendar. This may include complications that display sidereal time, equation of time, star chart, planetary positions, and other fantastically complicated celestial information.
Asymmetrical Case	A case shape that is asymmetrical. Sometimes a catchall term for all unconventional case shapes.
Asymmetrical Tooth Profile	Two gear tooth profiles in a single tooth cross section that are asymmetrical to each other. In watchmaking, there is a considerable minority of asymmetrical-profiled gears.
Atelier	(French) A workshop of an artist, artisan, or craftsman. In watchmaking, atelier refers to a workshop that is manned by not only the master craftsman but also several assistants.
Atelier de Terminage	(French) A factory or workshop which only assembles, times, and cases as opposed to producing any components or dealing with business and logistics.
Athletic Watch	A category of wristwatch designed for a specific sport. They are not as well-known as very few sports require dedicated timepieces. While there have been many historical designs for watches designed to withstand the shocks of intense sports, modern athletic watches are often born out of sponsorship deals with teams or star athletes. They are built of strong and lightweight materials with particular attention to shock resistance. Some have complications that assist with scorekeeping.
Atlas	A nickname for the Seiko 5 Sports SKZ2XX series expedition watches. The nickname likely comes from the watch's ability to assist in land navigation and map-reading. It is also known as the 'Landshark'.
Atomic Clock	A timepiece that measures time by monitoring the resonant frequency of atoms. Atomic clocks typically use cesium, rubidium, hydrogen, or strontium atoms with cesium’s only stable cesium-133 isotope being the most common choice. The typical atomic clock counts 9,192,631,770 vibrations of a cesium-133 atom when exposed to microwaves of the equivalent wavelength (9 GHz). The microwave wavelength is made accurate via a coupled quartz oscillator which is jolted to the correct frequency if the clock’s internal mechanism detects that the wavelength is off. An incorrect oscillator frequency leads to an incorrect microwave wavelength, meaning that the cesium atoms will not become excited. This means that the detector will not pick up the fluorescent signature of the excited atoms, leading to the jolt of electricity that triggers the quartz oscillator to return to the collect frequency and its connected microwave emitter to the correct wavelength. This feedback loop is self-correcting, making the clock very accurate.
Audemars Piguet	A watch manufacturer established in Le Brassus, Switzerland in 1875. Audemars Piguet is privately owned.
Auf	(German) 'Up'. Full Power.
Authorized Dealer (AD)	A distributor/retailer of watches that is officially sanctioned by the manufacturer to sell their watches to consumers. ADs can give discounts, deals, accessories, warranty, maintenance and repairs, and other services offered by the original manufacturer in addition to their own benefits. This distinguishes them from non-authorized dealers such as private sellers, second-hand sellers, and others who don't represent the manufacturer.
Automatic Movement	A movement which can be wound with an oscillating mass. Synonymous with 'self-winding movement'. Automatic movements convert the wearer's wrist activity to potential energy by using the rotor-weight to wind a spring (in a mechanical watch) or capacitor (in a quartz watch). Many automatic movements can also be manually wound. While automatic movements are usually mechanical, there are also many electronic movements that utilize automatic mechanisms to charge electrical capacitors. In the latter case, 'self-winding quartz', 'automatic quartz', or 'autoquartz' is used to distinguish these movements from the better-known mechanical automatics.
Avance	(French) Advance. Commonly written in full or abbreviated as 'A' on balance cocks for adjusting the regulator. Pointing the index towards A speeds up the watch.
B-Uhr	(German) Short for 'Beobachtungsuhr', or 'observation watch'.
Baby Grand Seiko	A nickname for the Seiko SARB03X series watches which have high quality finishing and resemble Grand Seiko sports watches, featuring similar dauphine hands, baton markers, case profile, bracelet, and dial composition.
Baby Jumbo	A nickname for the Seiko references 6139-7030/1 and 6139-7070/1 which closely resemble the 6138-300X series ‘Jumbo’ watches.
Baby Kakume	A nickname for the Seiko reference 6138-8030 which closely resembles the 6138-003X ‘Kakume’ series. One of the dial configurations of this reference is called the ‘John Player Special’ after the famous Rolex wristwatch which also sports a black and gold color scheme.
Baby Panda	A nickname for the Seiko reference 6138-8000 which closely resembles the 6138-8020 ‘Panda’. Like the Panda, the name ‘Baby Panda’ is derived from the look of the most famous watch that carries the reference and applies to all other dial configurations even if they are not panda dials. The famous Seiko ‘Reverse Baby Panda’ is also part of this family.
Backlash	The gaps or clearance between parts, particularly meshing gear teeth. Backlash is an important concept in watchmaking as the majority of wheels and pinions in a mechanical movement require a certain degree of backlash. In the absence of backlash, meshed wheels may jam and clutches may not engage. On the other hand, excessive backlash means that the watch will run too loosely, leading to unstable operation of moving parts, accelerated wear, and a general loss in reliability and accuracy.
Backlight	A light that illuminates an LCD from the back or side. Unlike LED displays, LCDs do not produce their own light and thus must be illuminated by an external light source to be read at night.
Balance	A device that is the timekeeping organ of a mechanical movement. The balance consists of a weighted wheel (balance wheel) and a spiral or helical torsion spring (called the 'balance spring' or 'hairspring') mounted at the wheel's center axis which allows it to rotate back and forth, or oscillate at a consistent frequency. This frequency, also called the 'beat' of the watch, allows the watch to keep time reliably. The balance's motions controls the rotation of the gear train via the escapement. Balance can also be short for 'balance wheel'.
Balance Bridge	A double-ended bridge that mounts the balance at its center. A balance bridge is anchored to the main plate on both ends unlike a balance cock which is anchored at only one end. Essentially a balance bridge is two conjoined balance cocks.
Balance Cock	A single-ended bridge that mounts the balance at its end. A balance cock is anchored to the main plate on only one side, with the other suspending the balance. Compare with 'balance bridge'.
Balance Spring	Also known as a hairspring. A spiral or helical torsion spring that allows the balance wheel to oscillate at a consistent frequency. The balance spring starts at the collet and terminates at the stud. Not to be confused with 'mainspring'.
Balance Staff/Shaft	The axle on which the balance wheel is mounted.
Balance Wheel	A spoked wheel that is weighted in order to oscillate at a consistent frequency with the assistance of the hairspring. A balance wheel may have different types of weight which control its oscillating rate and adjusts for factors such as temperature.
Bamboo Bracelet	A three-link bracelet consisting of one extremely wide but short center link and two narrow and short outer links, and a sliding clasp. The center links have spaces between them that allow a hooked beak in the sliding clasp to latch on. The bracelet was likely first made by American company Krementz & Co., which saw little success compared to an identical product sold by B. H. Britton & Sons as the 'Bonklip'.
Band	A component of a wristwatch that fastens the watch to the wearer's wrist. A band constructed of a pliable material such as leather, fabric, or rubber is often called a 'strap' while one constructed of metal parts is usually called a 'bracelet'.
Banking Detent	See ‘banking pin’.
Banking Pin	A pin which limits the range of motion of the pallet fork. Banking pins always come in pairs.
Bao Dai	A nickname for the unique Rolex Oyster Perpetual reference 6062 Triple Calendar in yellow gold with a gilt black dial with diamond indices specially made for the last emperor of Vietnam, Bao Dai (r. 1926-1945).
Bar	A component of a wristwatch that fixes the strap to the head, usually between the lugs. By far the most common type of bar is the spring bar.
Barometer	An instrument that measures atmospheric pressure. Barometers can be useful for determining elevation in the absence of a dedicated altimeter and for forecasting the weather.
Barrel	A hollow cylindrical container which houses the mainspring. The cavity of the barrel has enough space for the mainspring to be uncoiled and its circumference is lined with teeth to interact with the gear train and deliver power to the movement. A watch may have more than one barrel - and thus more than one mainspring - to increase its power reserve.
Barrel Case	See ‘tonneau case’.
Bart Simpson	A nickname for Rolex dials featuring a particularly fat crown resembling the head of Simpsons character Bart Simpson. The Bart Simpson dial marks the final iteration of the Rolex Oyster Perpetual Submariner references 5512 and 5513 to feature gloss gilt dials.
Batgirl	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 126710BLNR, a GMT-Master II with a black and blue Cerachrom bezel, blue GMT hand, and Jubilee bracelet. The name arose out of a need to differentiate it from its predecessor whose only cosmetic difference is the bracelet.
Batman	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 116710BLNR, a GMT-Master II with a black and blue Cerachrom bezel, blue GMT hand, and Oyster bracelet.
Baton Hands	A style of hands distinguished by long and slender hands with little or no taper. The tips of baton hands may be rounded or pointed. Baton hands may be lumed or unlumed.
Battery	A device that converts chemical potential energy into electrical energy. Batteries store energy in electrochemical cells, leading to slower charge and discharge times, steadier voltage, and longer-lasting discharge than a capacitor. Batteries may either be primary (single-use) or secondary (rechargeable). Batteries are the most common power source for electrically-powered watches. Some light/solar-powered watches use rechargeable batteries instead of capacitors. Also see ‘capacitor’.
Bauhaus	A style of visual arts, industrial design, architecture, and cultural movement spearheaded by the Staatliches Bauhaus in interwar Germany. Bauhaus epitomized the marriage of practical function and aesthetic beauty, imbuing functional objects with an uncluttered design with a reserved artistic flair that maximized their utility while also being beautiful. While short-lived and disorganized, Bauhaus had a tremendous influence on our world and continues to live on to this day. In watchmaking, Bauhaus is credited with the creation of the modern wristwatch as we known it as well as dial, case, and font designs that are ubiquitous even today.
Baume & Mercier	A watch manufacturer established in Geneva, Switzerland in 1830. Baume & Mercier is owned by Richemont.
Bayonet Caseback	A type of caseback that is fastened by flanges on the caseback locking into notches in the caseback opening. The mechanism is most reminiscent of a camera lens locking onto a DSLR body and somewhat similar to how a bayonet's notch engages with the bayonet lug at the end of a rifle. Bayonet casebacks are essentially screw-down casebacks with much beefier and shorter threading, which offers the security of the threaded caseback while preventing the possibility of cross-threading. Therefore they are excellent choices for dive watches. Bayonet casebacks frequently accompanied vintage Super Compressor dive watches but can still be found in many famous modern dive watches under various branded names.
Bead-blast	A type of abrasive blasting that blasts glass beads on a surface. The resulting finish has more sheen than the oft-compared sand-blasting.
Beads-of-rice Bracelet	A bracelet made of many small, vertically long, and horizontally narrow links that resemble grains of rice. They may be purely constructed of these links or have slightly differently-shaped outer links. Beads-of-rice bracelets were first constructed by Gay Frères. Due to their versatile look they are common choices for dress watches as well as dive watches.
Bean Lugs	A style of lugs that are straight lugs with a small curve towards the wrist, making the sides of the lugs resemble beans. Also see ‘fagiolino’.
Beast	A nickname for the Audemars Piguet Royal Oak Offshore reference 25721ST. The name is a reference to its massive dimensions and weight. Later on all Royal Oak Offshore watches with a chronograph would be called Beasts.
Beat	A semi-oscillation of a balance spring. It is so called because of the sound that the balance makes when reaching the end of its range of motion. A beat is important in mechanical watchmaking as it is counted to measure the frequency of a watch.
Beat Error	The time difference between beats, or semi-oscillations in a mechanical balance. It is measured in milliseconds (ms). The ideal beat error is 0, as it is ideal for each beat to immediately succeed the previous beat.
Beat Rate	A measurement of how many times the balance semi-oscillates, or ‘beats’, over a certain period of time. It is a common way to indicate the frequency of a mechanical balance. Beat rate is usually indicated as beats per second (bps), beats per minute (bpm), or per hour (bph). It can alternatively be measured in vibrations, which is completely interchangeable with beats. Also see ‘Hz’ and ‘vph’. Not to be confused with ‘rate’.
Beater Watch	A watch that is intended to be worn even at the risk of taking damage. Beater watches are typically chosen from exceptionally durable watches that can handle abuse. Many beaters are affordable to the owner as there is a higher risk that the watch may be damaged beyond repair or lost. This is not always the case as some watches command high prices for the same reasons they would be ideal beaters. Beaters should not be confused with throwaway or disposable watches.
Beauty	A nickname for the Audemars Piguet Royal Oak Offshore reference 25721BA. As the ref.25721BA was the first all-gold Offshore, it contrasted greatly with the steel original dubbed the ‘Beast’. Therefore the gold watch was nicknamed ‘Beauty’. Also see ‘Pounder’.
Bench	An article of watchmaking furniture that is used as a work surface for watchmakers. Benches are usually elevated to the watchmaker’s upper chest level to minimize hunching, and often have padded arm rests. Many come with drawers and cabinets to store to numerous tools and spare parts required for watchmaking.
Beobachtungsuhr	(German) Literally 'observation watch'. Commonly abbreviated as 'B-uhr'. In common English usage the term refers to a type of pilot's watches issued to certain members of the German Luftwaffe in WWII. However in German the term may broadly refer to a wide range of observation watches and clocks used for navigation and precise timekeeping. Also see 'Tensoku'.
Bertolli	A nickname for a variant of the Rolex Oyster Perpetual Submariner 16610LV ‘Kermit’ with a bezel of a lighter hue of olive green than standard. The nickname comes from the renowned brand of olive oil. On a side note, all Bertolli Kermits feature the ‘Flat Four’ because they were all produced before the Flat Fours were discontinued by a font redesign. Also see ‘Flat Four’.
Bevel Gear	A gear with slanted teeth arranged across a conical pitch surface. Two meshed bevel gears arranged perpendicularly are capable of transmitting mechanical power from a horizontal to vertical shaft or vice versa. Though not common in watchmaking, certain movements make use of bevel gears. Also see 'crown gear', which is a similar gear which transmits power to a perpendicular axis.
Bezel	The ring that frames the crystal of a watch. The bezel's function is sometimes to fasten the crystal of the watch, but may also serve other or additional functions such as protecting the crystal from impact, timing events, calculations, or decoration.
Bezel Insert	A ring-shaped component that fits onto a bezel to give the bezel color, a scale, or markers. A bezel insert can be identified by its having a different color or material from the outer rim of the bezel, e.g. a black stainless steel bezel or a ceramic bezel that is surrounded by a stainless steel bezel rim. Some watches have entire bezels made out of a different material (e.g. ceramic or gold) while others have markings directly engraved into the bezel. In these cases, the watches do not have bezel inserts.
BFK	'Big Fucking Kinetic'. A nickname for the Seiko SKA3X1 Kinetic divers, known for their large and chunky size.
Bi-color Bezel	A bezel, usually rotating, consisting of two colors. Bi-color configurations are commonly used for GMT bezels which distinguish between day and night hours and for diving bezels which often color the first fifteen or twenty minutes (a common dive time for dives at 30m below the surface).
Bidirectional Rotating Bezel	A bezel which rotates in both directions. Bidirectional rotating bezels are the norm for rotating bezels other than most diving bezels.
Big Block	A nickname for the Tudor Oysterdate chronographs of the 9400 and 79100 series. The name comes from the watch's large and blocky case to accommodate the automatic chronograph movement.
Big Blue	A nickname for the Omega Seamaster Planet Ocean GMT reference 215.92.46.22.03.001, which is a big and blue watch.
Big Crown (Rolex)	A nickname for the Rolex Oyster Perpetual Submariner references 6200, 6538, and 5510 owing to their oversized crowns which measure 8mm. Their large crowns were further accentuated by their lack of crown guards.
Big Eye	A nickname for a watch, especially a chronograph, with particularly large sub-registers. Famous big eye chronographs include models produced by Longines, Rolex, Universal Genève, and Enicar.
Big Eyes (Rolex)	A nickname for Rolex Daytona dials with larger-than-normal sub-registers, found on references 6263 and 6265.
Big Red	A nickname for the Rolex Cosmograph Daytona reference 6263 with an extra-large 'Daytona' written in red ink above the hour sub-register.
Bimetallic Balance Wheel	A balance wheel that is constructed of two different metals, usually brass for the outer layer and steel for the inner layer. The bimetallic composition allows the balance wheel to maintain a steady rate of oscillation in both hot and cold temperatures due to the different temperature coefficients of the two metals. Hairsprings tend to expand and contract depending on the temperature and brass reacts similarly, making them compatible for each other. The steel inner rim provides stability as pure brass would be too unstable and unreliable for timekeeping. Also called a 'self-compensating balance wheel'. As a bimetallic balance wheel has two cuts to allow the balance wheel arms to expand and contract, it is also called a 'split balance wheel'.
Bishop	A nickname for the Seiko reference 7A28-6000 and its reissue, SCED019 which was worn by Lance Henriksen as the android Bishop in the 1986 film Aliens. While the watch is sometimes called 'Giugiaro' after its designer, this name is taken by the more famous gray variant 7A28-7000 worn by Sigourney Weaver as Lieutenant Ripley.
Black Polish	A method of finishing and type of polishing where the metal surface is rubbed to such a smooth finish that the surface appears jet black from certain angles. Also known by its French name 'spéculaire' and as 'mirror polish' and 'block polish'. Black polish is laborious and difficult and thus typically associated with high horology.
Blancpain	A watch manufacturer established in Villeret, Switzerland in 1735 and now headquartered in Le Brassus, Switzerland. Blancpain is owned by the Swatch Group.
Blind Hole	A hole that does not completely penetrate and therefore has only one entry point. In watchmaking, a blind hole refers to a lug hole that does not extend to the outside surface of the lug. In this context it is antonymous to ‘drilled lug’.
Blitzende Sekunde	(German) ‘Flashing seconds’. See ‘foudroyante seconds’.
BLNR	Bleu, Noir. Rolex nomenclature for a blue and black bi-color bezel.
Blocking Lever/Chronograph Wheel Brake	A component of a chronograph mechanism which acts as a brake for the chronograph runner/chronograph wheel which controls the chronograph seconds and by extension the rest of the chronograph hands. The brake is a lever which is applied to the runner in its default state and can be lifted by
BLRO	Bleu, Rouge. Rolex nomenclature for a blue and red bi-color bezel.
Blueberry	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 1675 with a blue bezel. The watch was allegedly ordered for the United Arab Emirates Air Force. There is a substantial number of experts who believe that Rolex never made such bezels. The authenticity of the watch remains one of the most controversial and unresolved mysteries in the Rolex world to this day.
Bluesy	A nickname for the Rolex Oyster Perpetual Submariner references 16613, 116613, and 126613LB which feature a blue dial, blue bezel, and two-tone case.
Boiler Gauge	A dial configuration of the Rolex Datejust that features applied stylized Arabic numerals around a railroad chapter ring on an enamel dial. The Boiler Gauge is easily distinguishable by its quirky numeral font and its chapter ring which lies inside the ring of hour markers. The latter gives it its nickname as it resembles the steam pressure gauge of a boiler.
Bombay	A nickname for various Rolex Oyster Perpetual references in the mid-20th century that have bombé, or out-turned/twisted lugs. ‘Bombay’ is either a corruption or humorous misreading of ‘bombé’. Also see ‘bombé lugs’.
Bombé Lugs	(French) Bomb lugs. Another name for ‘twisted lugs’. The etymology is unclear.
Bonded Leather	A type of leather. Bonded leather is commonly understood as the least desirable kind of leather, with many considering it a non-leather product. It is constructed with leather scraps, shavings, and other normally disposed materials and put together with copious amounts of glue and plastic.
Bonklip Bracelet	A variety of bamboo bracelet patented by Dudley Howlitt of England and manufactured by B. H. Britton & Sons of London. Due to Britton's contract with the British Armed Forces, 'Bonklip' has become a household name as well as a byword for the bamboo bracelet.
BOR	Acronym for 'beads-of-rice'. See 'beads-of-rice bracelet'.
Bosley Regulator	A regulator that utilizes an index lever to adjust the curb pins and free length of the balance spring. Invented in 1755, the Bosley regulator is one of the most important and seminal regulator styles and is still widely used today. Most regulator designs are a variation of this system.
Boss	A nickname for the Seiko SKA2XX series Kinetic divers, known for their large and chunky size.
Bottle Cap	A nickname for the Seiko 5 Sports SRPC6X series watches whose flat profile and bezel notches make them resemble a crown cork bottle cap.
Bouchon	Synonymous with ‘bush’.
Box	The protective box that accompanies a watch.
Box and Papers	The state of having both the original box that the watch was delivered in as well as the appropriate documentation unique to a watch that has a matching serial number.
Boys' Watch	A watch designed with a boy or adolescent male in mind. Boys' watches share the design language of men's watches but come in considerably smaller sizes. The term is rarely if ever used today.
Bph	Beats per hour. A unit of measurement for frequency in movements with mechanical balances.
Bps	Beats per second. A unit of measurement for frequency in movements with mechanical balances.
Bracelet	A band made of metal. Usually a bracelet is constructed of many individual links which makes the bracelet flexible.
Bracelet Extender	A device that extends the wearable length of a wristwatch bracelet. Extenders are useful when the exact extra links are unavailable.
Bracelet Press	A press that is designed to remove or add the pins and collars to a bracelet.
Bravo Timezone	Military timezone name for UTC-2.
Brazed Lugs	Lugs which have a clear and visible brazing line between the base of the lug and case, or any lugs that are attached through brazing regardless of visibility. Brazing is a metal-joining technique where a molten filler metal of a lower melting point than the workpieces conjoins two unmelted workpieces. Brazed lugs are characteristic of earlier wristwatches of the early 20th century before the lugs could be machined together with the case or the joining techniques became more advanced. They are sometimes erroneously known as ‘blazed lugs’. Also see ‘soldered lugs’ and ‘welded lugs’.
Breguet	A watch manufacturer established in Paris, France in 1775 and now headquartered in L'Abbaye, Switzerland. Breguet is owned by the Swatch Group.
Breguet Dial	A dial with Breguet numerals. While a dial with other Breguet signatures such as a grand feu enamel or engine-turned finish may warrant the name, the term most commonly refers to a dial that has Breguet numerals.
Breguet Hairspring	See 'Breguet overcoil'.
Breguet Hands	A style of hands distinguished by a convex shaft with a curved taper, a ring towards the neck, and a triangular pointed tip, The Breguet hand can be considered a type of moon hand. The name originates from the hands' creator, legendary watchmaker Abraham-Louis Breguet. They were slightly modified variations of the 'apple hands', or aiguilles à pomme invented by Breguet's master Jean-Antoine Lépine. Breguet hands are not lumed.
Breguet Numerals	A style of Arabic numerals distinguished by calligraphic strokes of highly varied thicknesses and whimsical curves. Breguet numerals are traditionally painted onto an enamel dial but are also commonly fashioned out of metal and applied. The name originates from the numerals' creator, legendary watchmaker Abraham-Louis Breguet.
Breguet Overcoil	A bent, incurved terminal section on a coiled hairspring to improve isochronism in hairspring amplitude. In laymen's terms a Breguet overcoil refers to a hairspring with a bent end that coils over the rest of the concentric coils, which compensates for variations in amplitude and makes the balance run more evenly. Also known as the 'Breguet spiral', 'Breguet hairspring', 'Phillips terminal curve', 'terminal curve', and 'terminal coil'.
Breitling	A watch manufacturer established in Saint-Imier, Switzerland in 1884 and now headquartered in Grenchen, Switzerland. Breitling is owned by the Partners Group.
Brevet	(French) Patent.
Brick	A nickname for the Audemars Piguet Royal Oak Offshore reference 26470OR. The name is a reference to its immense weight and mega tapisserie dial which looks like a brick wall.
Bridge	A structural piece of a movement that is fastened to the plate on two ends. A bridge usually has a mounting point towards its center that can suspend a wheel of some sort. Bridges are generally more stable than cocks but occupy more space. Also see ‘cock’.
BRIL	Brillants. Rolex nomenclature for a bezel set with baguette cut diamonds.
Broad Arrow	A symbol that is an upwards-pointing tanged arrowhead, abstracted into three isosceles triangles converging at a single apex. In an even simpler form it may simply be three lines. The symbol is derived from a more figurative depiction of the arrowhead which is commonly used as a heraldic device. The broad arrow is used to mark property of the British government, especially the Ministry of Defense. Many watches issued by the British military had the broad arrow printed on the dial and/or engraved on the caseback.
Bruce Lee	A nickname for the Seiko 5 Sports reference 6139-6010 Speed-Timer automatic chronograph with a black dial, worn by martial arts legend, actor, and filmmaker Bruce Lee. The monicker 'Bruce Lee' is sometimes used more generally to refer to any chronograph in the 6139-601X family, which includes several other color variations.
Brushing	A method of finishing where a spinning wire brush is used to abrade the surface of metal to create unidirectional lines.
Bubbleback	A nickname for the numerous Rolex Oyster Perpetual references produced from 1933 starting with reference 1858 and ending at around 1964 with reference 6105. The name comes from the watch's prominently-protruding bulbous caseback which accommodates the extra height added by the automatic winding mechanism. The Italian nickname is 'Ovettone', which means 'big egg'. The Bubbleback was Rolex's first automatic watch. It gradually evolved into the Oyster Perpetual watches that still exist today.
Buckle	A component of a watch band that uses a loop and catch at the end of one piece to fasten the other piece. The buckle is one of the two major locking mechanisms for a band alongside the clasp. It is considered the most classic and simple locking mechanism for a wristwatch. Advantages of the buckle include simplicity, reliability, price, elegance, and ability to lay the watch flat on a surface. Disadvantages include incompatibility with bracelets, heavy wear on the strap material and adjustment holes, and increased risk of dropping the watch when putting it on. Also see 'clasp'.
Buckley Dial	A Rolex Oyster Perpetual Datejust or Day-Date dial with printed Roman numerals. The name comes from John Buckley, a watch dealer based in New York City who jokingly named these then-unpopular dials after himself as a jab at the haphazard naming conventions of dial configurations. The discussion forums promptly started calling these dials 'Buckley dials'.
Bulgari	A watch and jewelry manufacturer established in Rome, Italy in 1884. Bulgari's watchmaking is based in Neuchâtel, Switzerland. Bulgari is owned by LVMH Moët Hennessy Louis Vuitton.
Bullet	A nickname for the Seiko references SKXA53 and SKXA55 divers which have indices that resemble rifle bullets.
Bullet Lugs	A style of lugs that resemble a bullet. A pair of bullet lugs resemble two bullets headed in opposite directions, with the flat ends of the bullets accommodating the bar.
Bulletin de Marche	(French) A certification of accuracy issued by an astronomical observatory to a certain movement after accuracy testing. ‘Bulletin de Marche’ can translate to ‘Report of Operation’ or ‘Report of the Running (of the Watch)’. Bulletins de Marche are usually given to a single, serial numbered movement that was actually tested by the observatory.
Bullhead	In watchmaking, a 'bullhead' is any chronograph case that has its crown and pushers at the twelve o'clock position instead of the usual three o'clock position. The case profile is also often tapered, with a wider top end and narrower bottom end, further resembling the head of a bull. The bullhead chronograph can be chiefly seen in the catalogues of Seiko, Citizen, and Omega.
Bullhead (Seiko)	A nickname for the Seiko 6138-004X series automatic bullhead chronographs. Also see 'bullhead'.
Bullseye	A dial configuration that uses concentric circles of different colors to divide the dial space like a target, hence the name. The bullseye dial is similar to the sector dial, but the difference is that the bullseye dial emphasizes a difference in color for design while the sector dial emphasizes a clear separation of the minute and hour markers for legibility. The two are not mutually exclusive and it is common to see bullseye sector dials. Black and white bullseye dials are called ‘tuxedo dials’.
Bumper	A type of oscillating mass in an automatic mechanical movement that does not make a full rotation. Instead, it travels within a limited section of the circle. The name comes from how the weight bounces or bumps off of springs located at each end of its travel area. Bumpers are sometimes seen as antiquated and are rarely seen in modern watches.
Bumper Movement	A type of automatic movement which uses a bumper. See 'bumper'.
Bund Strap	A style of strap, usually leather, that employs a pad behind the watch that separates the caseback from the wrist. Bund pads are wide enough for the watch head to rest on comfortably and usually have a slit on each end or a loop through which the normal watch straps are pulled through. In the past the bund strap protected a non-water resistant watch from the wearer's sweat while also protecting the wrist from the caseback in extreme heat or cold. This was especially useful for tankers and aviators. However, the bund strap is usually a style choice.
Burke	A nickname for the Seiko reference H556-5050 ana-digi alarm chronograph worn by Paul Reiser as Carter Burke in the 1986 film Aliens.
Burnisher	A tool with a smooth surface that is used for polishing fine surfaces such as screw heads or studs.
Bush	A circular piece of (usually) brass that is intended reduce friction between a pivot and its hole by serving as the hole’s lining. Bushes often fulfill similar roles as pivot jewels but are cheaper and more resilient to damage. However, bushes are more susceptible to wear, which leads them to be used for pivots that do not rotate as much.
Bushing	Synonymous with ‘bush’.
Bust Down	Slang for a watch with an aftermarket diamond-setting job. It is antonymous to ‘factory’ in this context.
Butterfly	See ‘Morpho’.
Butterfly Clasp	Another word for a double-fold clasp. Its name comes from how the clasp opens on both sides like a butterfly spreading its wings. Also see 'double-fold clasp'.
Button Compass	A small compass in the shape and size of a large button that is meant to be attached to a watch band. Button compasses have been common accessories for alpinists, soldiers, navigators, and explorers due to their convenience. While not as accurate as full-sized compasses, button compasses are easily accessible. They are also loved for their aesthetic.
Cabochon Crown	A style of jeweled crown distinguished by a cabochon, or a polished and unfaceted jewel.
Cadrature	(French) Also known as 'under-dial work' in English. Mechanisms and clockwork for a specific purpose, especially for repetitions. In modern usage it is treated as a somewhat antiquated synonym for 'module'.
Caesar	A nickname for the Seiko references SNDA13/15 (quartz) and SKA383/385 (Kinetic) divers whose huge case size probably granted them the nickname 'Caesar'.
Calatrava (fortress)	The Spanish adaptation of Arabic 'Qal'at Rabah', or 'Fortress of Rabah'. Calatrava is where the Spanish repelled the Moors in 1158, prompting the establishment of the Order of Calatrava symbolized by the Calatrava Cross. In watchmaking, this name is famous due to Patek Philippe. Also see 'Calatrava Cross', 'Calatrava (wristwatch)', and 'Calatrava (style)'.
Calatrava (style)	An unofficial catchall name for a group of wristwatches that reflect the design features of the Patek Philippe Calatrava wristwatch. It refers particularly to the case design, namely a case with a thin profile, slab-sided flanks, gently tapering lugs naturally sprouting out from the case flanks, and a simple round bezel. Also see 'Calatrava (wristwatch)'.
Calatrava (wristwatch)	A family of wristwatches manufactured by Genevan watchmaker Patek Philippe. Launched in 1932 as the reference 96, the Calatrava is one of the most influential wristwatch designs in history. The Calatrava was designed with Bauhaus principles and pioneered gently tapering integrated lugs that flow naturally from the case flanks and a round dial with practical and legible markings. In an era where wristwatches were relatively new and many designs were simply afterthought modifications of small pocket and pendant watches, the Calatrava set the blueprint for wristwatch design forever and remains a universally respected icon of quietly elegant design. Also see 'Calatrava cross' and 'Calatrava (style)'.
Calatrava Cross	A type of cross, in the form of a Greek cross with a fleur-de-lis at each end. It served as a symbol of the Order of Calatrava, a Spanish religious and military order. In watchmaking it is famous as the symbol of watchmaker Patek Philippe, and as an eponymous family of dress watches produced by the company. Also see 'Calatrava (fortress)', 'Calatrava (wristwatch)', and 'Calatrava (style)'.
Calendar	A system of organizing periods of time, typically into days, weeks, months, years, etc. See ‘calendar complications’ for the application of calendars in watchmaking.
Calendar Complications	A family of complications that concern the tracking of days, weeks, months, years, and other units and periods of time in the human calendar. This includes simple complications like a date complication and high complications like perpetual calendars.
California Dial	A dial style that combines Roman and Arabic numerals. California dials often incorporated diver style indices into the mix to mark the four cardinal indices. The etymology is debated. These dials were also called 'error-proof' dials.
Calipers	A device used to measure the dimensions of an object. Most calipers in modern watchmaking are vernier calipers. Calipers are used to measure important dimensions on a watch like lug width, lug-to-lug, case diameter, dial diameter, buckle width, etc.
Caller/Office GMT	A GMT that has an independently-adjustable GMT hand. This configuration is useful to people for whom local time is home time (i.e. they are in their home time zone) but need to read the time of a second time zone for business calls or contact with family, hence the name 'caller' or 'office' GMT. The caller GMT is not as suited for traveling compared to the traveler GMT as adjusting the regular display to the local time requires the watch to be reset. While the wearer can use the GMT hand to reference local time, it is more difficult to read. Also see 'traveler GMT'.
Cam	A rotating piece that transforms rotary motion into linear motion.
Cam Chronograph	A chronograph which utilizes a shuttle cam or a similar system as its control system. Cam chronographs are far simpler than the column wheel chronographs before them and are reputed to be more rugged and reliable, cheaper to manufacture, and more tolerant to manufacturing irregularities. With modern manufacturing technology, the difference in reliability between column wheel and cam chronographs have been reduced. This has also brought significant improvements to the previously rougher pusher feel of cam chronographs, further leveling the two. Therefore, cam chronographs are often chosen for their cheaper manufacturing cost and simpler mechanics. Also see ‘column wheel chronograph’ for comparison.
Cam-poised/Inertia/Masselotte Balance	A balance wheel that is adjusted with disc-shaped inertia weights which are also called inertia blocks or masselottes.
Campaign Clock	See ‘carriage clock’.
Campaign Watch	A name for early wristwatches that were used in the British colonial campaigns of the late 19th century and the First World War.
Cannon Pinion	A component of the motion work which is mounted on the central axis of the watch (the center stack) and translates the movements of the wheels to the hands. It is directly controlled by the second wheel of the movement and thus completes a rotation every hour. Hence, the minute hand is directly mounted to the cannon pinion. The cannon pinion also indirectly controls the hour hand via a reduction drive called the 'motion work'. The cannon pinion is made up of a hollow shaft or pipe with a pinion fused to the base. The shaft is fitted to the center wheel arbor. Its name comes from the appearance of its long hollow shaft which resembles the barrel of a cannon. Also see 'motion work'.
Cap Gold	See 'gold-capped'.
Capacitor	A device that stores electrostatic energy by accumulating charges on an electrical field in the form of thin sheet metals separated by dielectric insulators. Capacitors store electrostatic energy in electrical form, leading to much faster charge and discharge speeds than a battery which contains potential energy in chemical form which must be converted to electrical energy. In watchmaking, capacitors are used in many rechargeable electrically-powered watches such as automatic quartz and light/solar-powered watches. Also see ‘battery’.
Captain Willard	A nickname for the Seiko reference 6105-8110 diver and its various modern reissues. The watch was worn by Martin Sheen as Captain Benjamin Willard in the 1979 film Apocalypse Now, a reflection of the fact that American soldiers in Vietnam often wore the 6105. The 6105 is also called the 'Uemura', after a Japanese explorer. See 'Uemura'.
Carage Case	A case shape distinguished by a horizontally long oval profile.
Carillon	In watchmaking, a carillon is an assortment of hammers and gongs which is capable of making at least three distinct pitches. This can be achieved with having three gong springs each tuned differently, or by having differently tuned hammers striking the same gong spring. Carillons are rare in watchmaking as only two pitches are needed to make three distinct sound signatures (dong, ding, ding-dong), but are highly valued for their ability to play complex chimes such as the Westminster chime.
Carré Case	(French) A square case.
Carré Galbé	(French) Curved square. A case shape which is more-or-less a square or stout rectangle with rounded edges. Several carré galbé cases feature subtle inward curves on the case flanks. In Italian, this case style is often called ‘cioccolatone’.
Carriage Clock	A clock style with a box (traditional) or cylindrical profile, footed base, and a carry handle. Invented by Abraham-Louis Breguet for Napoleon for his military campaigns, this style of clock is also called the ‘campaign clock’.
Cartier	A watch and jewelry manufacturer established in Paris, France in 1847. Cartier's watchmaking is based in La Chaux-de-Fonds, Switzerland. Cartier is owned by Richemont.
Carved	A component is carved when it is carved, etched, engraved, or otherwise cut into the dial surface.
Case	The housing of all the components of a clock. Cases are usually crafted out of a metal.
Case Cushion	A soft surface for a watch to be placed. Case cushions are particularly useful in supporting the watch when it is under a press.
Case Diameter	The diameter of a round wristwatch case. The case diameter refers to the distance of one extremity of the case flank to the other, excluding protrusions such as lugs, pushers, crown guards, etc. It is the most commonly used metric for measuring watch size, though it can be deceiving due to other measurements such as dial diameter and lug-to-lug. Case diameter is not used for shaped cases.
Case Flank	Also called the 'side case' or 'case side'. The side profile of the case of a watch.
Case Knife	A bladed tool that is designed to open snap-on casebacks. The blade is usually blunt and made of a soft metal or plastic as to avoid damaging the case.
Case Shape	The geometric shape of a case, referring to only the main case and not the lugs unless they are integrated into the design. In the rare instances where the dial shape does not match the case shape (e.g. round case with a rhombus dial or a square case with a round dial), the two should not be confused. Case shapes are largely divided into round cases and shaped cases, the latter referring to any case that is not circular.
Case Style	The aesthetic style of a case, typically referring to the case in its entirety including the lugs and sometimes the caseback. Case styles are often named after famous and influential designs. Some examples include the Calatrava (Patek Philippe), Oyster (Rolex), Clamshell (Gallet), and Tank (Cartier) cases. Sometimes case styles are named after famous casemakers such as Spillmann, Borgel, and Hagmann. They may also be named after certain defining features such as stepped case (case with a stepped bezel), tre tacche (caseback with three notches, usually also with a stepped bezel), and savonnette (pocket watch with front cover).
Case Wrench	A caseback opener in the form of a clawed wrench designed to open screw-down casebacks. The wrench usually has three teeth that can be adjusted with screws. The teeth made be made of hardened plastic or metal. While wrenches are the best way to open tight screw-down casebacks, poor contact with the notches or grooves in the caseback frequently result in gashes and scars.
Caseback	The backside of a case. The caseback is usually a removable lid which allows access to the movement for basic repairs. In so-called 'monobloc cases' the caseback is not a separate component but rather simply the backside of the case.
Caseback Opener	A tool that is designed to open casebacks. Due to the wide variety of caseback types, there are different openers for each style. Snap-on casebacks are usually opened with a knife. Screw-down and bayonet casebacks are typically opened with a wrench, friction ball, or a dedicated tool. Screw-in casebacks are opened with a screwdriver.
Caseback Press	A press that is designed to open and close casebacks. The presses can come in various forms fitted to different types of caseback. Caseback presses are particularly useful for safely opening and closing screw-down casebacks as they provide a stable purchase on the watch and the rotating opener, minimizing the risk of slipping and scratching the caseback.
Casemaker	An individual or production facility that specializes in the fabrication of cases.
Casemaker's Mark	A mark that symbolizes an individual casemaker or casemaker company. Not all watches have a casemaker's mark but they can often be found on the inner surface of the caseback. Some guilds have a numerical system which designates a unique number to each registered casemaker.
Casio	A watch manufacturer established in Tokyo, Japan in 1946. Casio is owned by the Casio Group.
Casio Royale	A nickname for the Casio AE1200 series worldtimers. The origin of the nickname is likely the 1967 James Bond film Casino Royale, but the watch did not exist then nor did James Bond ever wear a Casio. It is likely a reference to the watch’s similarity to the Seiko G757 Sports worn by Roger Moore in the 1983 James Bond film Octopussy.
Casioak	A nickname for the Casio G-SHOCK 2100 series watches. It is a tongue-in-cheek name that pokes fun at the watches' resemblance to the Audemars Piguet Royal Oak. Also see 'Royal Broke'.
Casting	A metalworking technique that involves the pouring of molten metal into the cavity of a mold. Casting is an extremely uncommon method in watchmaking because it is time-consuming and not intricate enough. In some limited instances, lost-wax casting or investment casting is used to produce cases. See ‘lost-wax casting’.
Catch and Release	Watch collecting parlance for selling a watch not long after purchase because of buyer’s remorse. Not to be confused with ‘flipping’, which is the act of selling a watch immediately after purchase for profit.
Cathedral Hands	A style of hands distinguished by broad surfaces usually filled with copious amounts of lume that is divided into sections which make the hands resemble stained glass windows on cathedrals. The walls between the lume pools also resemble the veins of a leaf. A cathedral hour hand is usually spade-shaped and feature elaborate veins. The minute hand is plume-shaped and feature simple, horizontal divisions. The seconds hand is normally tip with a diamond-shaped lume plot but may not be lumed at all. Cathedral hands were among the first style of lumed hands and were thus frequently used in military watches. They are still a common sight on vintage-inspired watches today. Cathedral hands are typically lumed.
Center Link	The link that is at the center of a bracelet.
Center Seconds	A type of seconds hand which is mounted on the center stack and whose range of movement occupies the entire area of the dial. Center seconds offer superior legibility and are particularly crucial for watches focused on high accuracy or intended for some form of measurement. Some experts consider it a complication as the natural position of the seconds hand follows the location of the fourth wheel, which is mounted off-center. This requires an addition of a gear train to 'move' the seconds hand to the center of the watch. However, this is no longer common due to fundamental changes in wheel train arrangement. See 'indirect center seconds' and 'direct center seconds'.
Center Stack	The handstack at the center of a clock. Clocks that do not have the traditional concentric layout (such as regulators) do not have center stacks.
Center Wheel	The wheel of the going train located at the center of the movement and dial. In a typical movement the second wheel serves as the center wheel. However, for certain movements the fourth wheel is moved to the center. Some movements may not have a wheel at the center at all.
Center Wheel Arbor	The arbor that lies at the center of a typical mechanical movement, primarily mounting the second wheel (center wheel). The arbor also mounts the important cannon pinion, and by extension the minute hand, hour wheel, and hour hand. In certain designs, it would also mount the fourth wheel and seconds hand by extension.
Central Chronograph Display	A chronograph whose chronograph hands are mounted to the center stack instead of inside sub-registers. This configuration is standard for the chronograph seconds hand because a centrally-mounted hand is far easier to read. However, some chronographs feature centrally-mounted chronograph minute hands as well. The tradeoff for superior legibility is the potential for confusing the chronograph hands with the regular hands.
Central Rotor	A type of oscillating mass in an automatic mechanical movement that is mounted on the center of the movement and utilizes the entire circumference of the movement as its travel distance. The central rotor is by far the most common type of oscillating mass. A central rotor is simple and efficient but adds height to the movement as it requires an extra layer.
Centrifugal/Fly Governor	A governor for a striking train which employs a spindle with two weighted arms to regulate the strike tempo. The extent to which the arms are allowed to move when the spindle is in motion determines the speed of the striking train. This distance can be adjusted to make the repeater train go faster or slower.
Cermit	A nickname for the Rolex Oyster Perpetual Submariner reference 126610LV, a Submariner with a green Cerachrom bezel and black dial. The name is a portmanteau of 'ceramic' and 'Kermit', the latter being the first Submariner to have a green bezel. This reference is also called the 'Starbucks' due to its having a noticeably different shade of green from the lime green of the Kermit. However, the updated color on the 126610LV starting from 2023 (the 70th anniversary of the Submariner and 20th anniversary of the Kermit) has started a differentiation between the more hunter green Starbucks and the more lime green Cermit. The updated 126610LV now sports a green that is much closer to the original Kermit, the only major cosmetic difference being the use of a ceramic bezel insert instead of an aluminum one.
CERN (Rolex)	A nickname for the first variant of the Rolex Oyster Perpetual Milgauss reference 1019 which features a non-lumed dial believed to be ordered by the European Organization for Nuclear Research, or CERN (Centre Européen de Recherche Nucléaire). The non-luminous dial was requested because the tritium lume would interfere with radioactivity readings. While the Milgauss was indeed developed at the request of CERN, the story behind the first generation dial is not completely confirmed.
Certificate of Authenticity	A document certifying the authenticity of a watch in part or in whole. A certificate can be issued on request of an individual from the manufacturer as most watches do not come from the factory with such a certificate (it is redundant with the original documentation which serves as a proof of authenticity anyway). A certificate of authenticity can be a suitable replacement for a lost original document containing the watch’s serial number(s). Manufacturers who do issue these certificates require the watch to be physically submitted to their facility for inspection. Alternatively, some third-party organizations and jewelers may certify the authenticity of a watch with varying levels of reliability. It should be noted that not all manufacturers provide this service and that even those who do may not accept vintage watches. Certain retailers and jewelers who carry the brand may offer this service independent of the manufacturer.
Cesium/Caesium (Cs)	Spelled ‘cesium’ in American English and ‘caesium’ in British English. An element used in the timekeeping organ of an atomic clock. Its single stable isotope, cesium-133, is the key element of an atomic clock and is used in the SI definition of a second.
Cevert	A nickname for the Seiko 6139-600X series automatic chronographs with blue dials. These watches are also called ‘Blue Pogues’ as ‘Pogue’ is the most widely accepted name for the entire 6139-600X series. The name ‘Cevert’ is an homage to François Cevert, a French Formula One racing driver who wore the blue-dialed 6139-6009.
Chablon	(French) An unassembled movement. ‘Chablon’ normally means ‘stencil’.
Chaîniste	(French) A maker of fine chains, especially for pocket watches.
Chamfering	A method of finishing where a right-angled corner is ground to a 45 degree bevel and highly polished. Also known by the French term ‘anglage’. Also see ‘beveling’.
Champlevé	(French) A decorative technique where vitreous enamel is poured into carved or cast recesses on a surface. It produces a similar effect to cloisonné, albeit with an opposite technique - in cloisonné the surface is merely lined with metal to provide compartments for the different colors whereas in champlevé the colors are poured into recesses cut into the metal. Usually the immediate giveaway is that cloisonné has more visible colors interspersed by metal linework while champlevé is mostly metal with portions of color. This is not always accurate, however. Moreover champlevé is a strictly enamel technique whereas cloisonné is a broader term that includes coloring with gemstones and pieces of solid glass.
Chapter Ring	The ring of hashes, indices, markers, or other indications that are graduated to show the minutes and seconds. Synonymous with 'minute track'. In Rolex parlance, a chapter ring is a minute track whose hashes are all connected to an outer ring. Meanwhile in Seiko parlance, the chapter ring is very often confused with the 'rehaut', which is the wall surrounding the dial of a watch. This may be because chapter rings in Seiko dive watches are often mounted on rehauts. It should be noted that both Rolex and Seiko-specific understandings of the word are incongruous with its actual definition.
Charlie Timezone	Military timezone name for UTC-3.
Cheville	(French) Short for ‘cheville de plateau’, ‘plateau’ being the French term for the roller. See ‘impulse jewel’.
Chevron Dial	A dial configuration of the Rolex Oyster that is divided into quadrants with diagonal hatching towards the center of the dial. The hatching resembles a stack of chevrons, hence the name.
Chime	A series of strikes, sometimes arranged into a melody.
Chinese Day Wheel	A day wheel with the days of the week written in Chinese. As most Chinese languages count days using numbers, the days are numbered (in Chinese characters) 1 to 6 for Monday to Saturday and the character for 'sun' for Sunday. Some non-speakers confuse the Chinese day wheel with the more famous Kanji day wheel. While both are written in Chinese characters, the day systems are completely different save for the character for Sunday.
CHNR	Chocolat, Noir. Rolex nomenclature for a brown and black bi-color bezel.
Chopard	A watch and jewelry manufacturer established in Sonvilier, Switzerland in 1860 and currently headquartered in Geneva, Switzerland. Chopard is privately owned.
Chronograph	A stopwatch. A chronograph is a mechanical complication that records elapsed time. In modern usage any watch with a stopwatch function can be called a chronograph. Not to be confused with 'chronometer', which is a term for a precise timepiece.
Chronograph Bridge	A component of a chronograph mechanism which is a bridge, usually shaped like a Y, which mounts the chronograph runner and minute recording wheel. Some watches have separate bridges for the two wheels. The chrono bridge typically occupies the center of the movement and sits right above the balance. It is one of the key defining visual features of a chronograph movement.
Chronograph Runner/Wheel	A component of a chronograph mechanism which operates the chronograph seconds hand. The chronograph runner derives its energy and rotation speed from the coupling wheel, which in turn is controlled by the driving wheel, which in turn is controlled by the fourth wheel. The runner has a sixty-second finger which initiates the minute recording wheel to move once every minute. The chronograph runner can be easily identified as it occupies the center of the movement and is mounted on the prominent chronograph bridge.
Chronometer	A precise timepiece. A chronometer is any timepiece that is very accurate according to a set of standards. Most timepieces are awarded chronometer status by various third party testing organizations such as COSC. Not to be confused with 'chronograph', which is a timing complication akin to a stopwatch. See also 'marine chronometer' and 'observatory chronometer'.
Chronometry	The science of timekeeping and its standards. In the past, the term 'horology' was used to this effect but has since changed to refer to the study of timekeeping devices, many of which are considered obsolete by modern institutional timekeeping standards.
Cioccolatone	(Italian) Big chocolate. In the Italian watch collecting community, ‘cioccolatone’ is a nickname given to square or stout rectangular watches for their resemblance to big pieces of chocolate. In the Anglosphere, the name is mostly associated with the Vacheron Constantin reference 4737 which features a carré galbé (curved square) case.
Citizen	A watch manufacturer established in Tokyo, Japan in 1918. Citizen is owned by the Citizen Group.
Civil Time	Statutory time commonly used and understood by civil society. Civil time is usually set by national institutions as a positive or negative offset of UTC (Coordinated Universal Time). Civil time may be different from time standards used by certain industries or professions such as navigation, geodesy, engineering, astronomy, and physics.
Clasp	A component of a watch band that opens and closes to enlarge and tighten the band. The clasp is one of the two major locking mechanisms for a band alongside the buckle. A clasp is distinguished by its use of locking and releasing metal parts as apposed to a buckle where the pin/tang fastens to a simple hole. The vast majority of clasps also perpetually connect the two ends of the band unlike a buckle where the two ends are separated when not on the wrist. Some advantages of the clasp are its sturdiness, ability to reduce wear on a strap, and lower risk of dropping the watch when putting it on. Disadvantage include comfort, weight, price, and inability to lay the watch flat on a surface without removing the clasp. Naturally, all bracelets are only compatible with clasps with the exception of a few strap-style bracelets that may use a tang buckle or sliding buckle. Also see 'buckle'.
Clepsydra	Synonymous with 'water clock'.
Click	A movable lever that engages a moving component to allow motion in only one direction and prevent it in the other. In industrial parlance, 'pawl' is the more commonly used synonym. In watchmaking, 'click' is more common. Clicks can be spring-loaded at the pivot. They can also be pressed down by a flat spring called a click spring. In some cases, the end of a click spring acts like a click. Together with the ratchet wheel, the click forms the ratchet mechanism.
Click Bezel	A rotating bezel that has a clicking action with tangible steps or clicks. Click bezels are fitted on top of a click spring, a circular wire spring with at least one curved end that engages with the tooth-lined interior wall of the bezel. The click spring's purpose is to provide resistance to the action so that it advances in clicks. Depending on the shape of the spring a click bezel can be engineered to be unidirectional or bidirectional. Also see 'friction bezel'.
Click Spring	A spring which maintains pressure on the click or acts as a click, usually in a ratchet assembly. When used in conjunction with a pawl or click, it maintains pressure on the click so that it seats properly at root of a gear tooth. This is common for the barrel assembly. When used as a click (usually with an annular/internal gear), a click spring is bent against the desired direction so that a tooth turning in that direction will simply push the bent end down. If it attempts to move the other way it will have the end of the spring stuck in its root. This is useful in unidirectional rotating bezels. Sometimes click springs are used for other purposes. In many bidirectional bezels, the click spring is bent so that the teeth on the inner gear can move when sufficient force is applied. This allows the bezel to stop precisely where it needs to, prevents it from wobbling or moving too much, and provides satisfying tactile and auditory feedback.
Clock	A device that measures and/or indicates time. Synonymous with 'timepiece'.
Clockwork	The mechanics of a clock or similar devices. Usually refers to mechanical devices. The term is more general than 'movement' and can include the assembly of gears, springs, levers, and/or weights used to power non-timekeeping objects like music boxes or wind-up toys.
Cloisonné	(French) A decorative technique where colored material is outlined with (usually precious) metal. While cloisonné may incorporate any colored material including gemstones, paint, and glass, in watchmaking the term is generally associated with vitreous enamel. Cloisonné is most commonly seen on dials and uses colored vitreous enamel and gold wire. The term comes from the French word 'cloison' (partition) which refers to the metal linework which demarcates the compartments of colored material. Also see 'champlevé' for a similar technique.
Club-tooth Gear	A gear with asymmetrically-profiled teeth which slope in one direction and peak at a hook. Club-tooth gears usually serve as escape wheels in Swiss lever escapements.
Clutch	A mechanism that allows the rotating input shaft to disconnect from the output shaft, or vice versa. In watchmaking, clutches are primarily used in chronographs and can either be horizontal or vertical. They are also sometimes used in winding mechanisms to prevent overwinding.
Co-axial Escapement	An escapement that utilizes two co-axial balance wheels with an ultimate goal of increasing precision and longevity by reducing friction. The co-axial escapement utilizes two balance wheels to engage four pallet jewels, dividing the roles of impulse action and locking action to one pair of pallets each. Several factors lead to reduction of friction. First, as one of the pallets is located directly on the roller, the impulse delivery is more direct. Second, the division of roles means that a pallet jewel does not need to advance the tooth of the escape wheel via sliding against it. Previously this was because the jewel also needed to be shaped to lock the tooth. This allows the pallet to push directly on the tooth, reducing a great deal of sliding friction. Third, the reduced friction reduces the need for lubrication, which may have an adverse effect on accuracy in the long run.
Co-branded	A watch is co-branded when it carries the emblem or name of a company other than the manufacturer of the watch and/or its components. Co-branding is slightly different from double-signing which is limited to retailers and jewelers who add their own logos to watches they sell. Co-branding is far broader and can include watches that are made in collaboration with or for corporations, government agencies, and trademarks. For example, the famous Rolex Oyster Perpetual watches with the Domino’s Pizza logo on the dial are co-branded, but not double-signed.
Cock	A structural piece of a movement that is fastened to the plate on one end. The other end usually mounts a wheel of some sort. Cocks are space-efficient as they are shorter than bridges which are fastened at both ends. However, they are generally not as good for shock absorption. The most famous cock is the balance cock, which suspends the balance assembly. Also see ‘bridge’.
Cocktail Watch	A category of wristwatch designed for high society ladies to complement their formal evening dress, particularly in the 1920s. Cocktail watches are distinguished by their diminutive size, elaborate diamond-studded case, and thin satin strap or bracelet. They almost invariably came as two-handers as the size was too small to accommodate even a seconds hand.
Coke	A nickname for a bi-color bezel consisting of black and red. It is most famous as the nickname for the Rolex Oyster Perpetual GMT-Master II reference 16760, a GMT-Master II with a black and red aluminum bezel and red GMT hand. The watch was also dubbed the 'Sophia Loren' and 'Fat Lady' for its large case.
Collet	A ring to which the inner end of the balance spring is pinned. The collet connects the balance spring to the balance staff.
Column Wheel Chronograph	A chronograph which utilizes a column wheel as its control system. Column wheel chronographs are reputed to provide a smoother and satisfying pusher feel and are seen as more refined and beautiful due to the aesthetic design of the column wheel and the various levers and hooks that engage with it. Column wheel chronographs have more complex mechanics and thus have tighter tolerances. However, with modern manufacturing technology, the reliability of the average column wheel chronograph has improved significantly and can be found on higher-end chronographs. Also see ‘cam chronograph’ for comparison.
Column Wheel Hook/Operating Lever Click	A component of a chronograph mechanism in the form of a hook/beak/click which snags the ratchet teeth of the column wheel and advances it forward. The hook is connected to the column wheel lever by a pivot.
Column Wheel Pawl	A component of a chronograph mechanism which applies constant pressure to the column wheel so that the wheel turns in the desired manner and is stationary otherwise.
Column/Pillar Wheel	A chronograph control system which takes the form of a ratchet wheel with an extra ring of raised trapezoidal teeth that resemble battlements. The ratchet teeth engage with the operating lever click/column wheel hook which advances the column wheel clockwise. The column wheel moves one click every time the chronograph is started or stopped. The castellated column teeth engage with fingers of various levers. Upon the push of the start/stop pusher, the column wheel moves a click and pushes the finger of the chrono wheel brake which frees the chrono runner while simultaneously allowing the finger of the coupling lever to fall between the column teeth and pivoting the coupling lever so that the coupling wheel attached to it connects the driving wheel and chrono runner. Stopping is simply the reverse. The column wheel also blocks the reset lever from moving when the chronograph is running. When the chronograph is stopped, the column wheel allows the reset lever to move through the space between its columns.
Compass	An instrument that points to magnetic north and the three other cardinal directions. Compasses are used to determine orientation and bearings in navigation.
Compax (general)	‘Compax’ is a confusing and often misused term. The term can refer to a specific chronograph made by Universal Genève and the subsequent series of chronographs that came after it (see ‘Compax (Universal Genève), watches that use UG Compax movements, watches that look like a UG Compax, or a numbering system for sub-registers on watches. The last use is technically incorrect, as the Compax numbering system was [number of sub-registers - 1] because it counted complications, not sub-dials (one sub-dial was always for the running seconds). Nonetheless, it is now popular to call chronograph dial configurations bi-compax, tri-compax, or quadri-compax depending on its sub-dial count.
Compax (Universal Genève)	A branded term for a wristwatch that has one or more complications, starting from a chronograph. The term was coined by Universal Genève and adopted by the many companies that purchased UG movements. Thus Compax is used mostly for UG watches or watches that use UG movements. The original Compax was a triple-register chronograph. After this, UG started adding number prefixes, which show how many complications there are. For example, a Uni-Compax has one complication: the chronograph. UG never made a Bi-Compax but did make a Tri-Compax with a chronograph, moonphase, and calendar. Also see ‘compax (general)’.
Compensating Balance	See ‘bimetallic balance wheel’. Also known as a ‘self-compensating balance’ or ‘compensation balance’.
Compensation Balance	See ‘bimetallic balance wheel’. Also known as a ‘self-compensating balance’ or ‘compensating balance’.
Complete/Full Calendar	A simple calendar complication that displays the date, day, month, and moon phase. It is a triple calendar with a moon phase complication. However, the distinction between a triple and complete calendar is hazy and many use the two terms interchangeably. The complete/full calendar is sometimes confused with the perpetual calendar due to their visual similarities. The major difference is in the mechanics and the existence of a leap year indicator.
Complication	In watchmaking, a complication is any mechanical feature of a timepiece that performs a function beyond the display of hours, minutes, and seconds. Typically, for a feature to be recognized as a complication it must have two attributes: one, it must be mechanical and not activated by electronics and two, it must be mechanically integrated within the movement. Therefore, features on a quartz watch are not generally regarded as complications. Neither are features such as a rotating timing bezel, compass, humidity indicator, or thermometers. Nonetheless, there is still great debate on what mechanical features can be considered complications. Complications can be divided into many families depending on their purpose, even though there is no consensus on the precise taxonomy.
Compressor	A subcategory of dive watch that utilizes the special compressor or super compressor case, or a watch that mimics the style of such a watch. The latter is more accurately called a 'compressor-style diver'. Compressor divers typically feature two crowns, one for the usual crown functions and an extra to operate the rotating internal bezel. While there is no rule that compressors must be dual-crowned and have an inner bezel, these patented cases were delivered to their clients that way and have thus become a part of the compressor look.
Compressor Case	A type of dive watch case whose caseback is sealed increasingly tighter by water pressure. Compressor cases use spring-loaded casebacks that only become as watertight as they need to be. They feature snap-on casebacks which were almost immediately followed up with screw-down casebacks in the newer super compressors. Also see ‘super compressor case’ and 'compressor'.
Concertina Hands	A style of hands distinguished by their ability to contract and expand depending on their position in order to reach the markers of an oval dial. The hands are essentially scissors mechanisms with multiple articulating joints that are manipulated by oval cams on the center stack. This allows the hands to contract when passing through the minor axis areas and expand when passing through the major axis areas. The name comes from how the scissors mechanism resembles the bellows of a concertina or accordion. Concertina hands are incredibly rare.
Conical Crown	A style of crown distinguished by deep fluting and a conical profile culminating to a flat or slightly bulbous top. Conical crowns are usually oversized and easy to grip as they were designed for aviators who were operating the crown with gloved hands. Therefore conical crowns are a common feature of pilot's watches. Often confused with the similar 'onion crown', which looks similar and serves the same purpose.
Connie	A nickname for the Omega Constellation.
Constant Force Mechanism	A mechanism which evens out the variable force released by the unwinding of the mainspring. The force and torque of the mainspring influences the beat rate of the watch which ultimately affects its accuracy. A constant force mechanism acts as a mediary between the mainspring and escapement. This can be achieved in many ways including an extra intermediary escapement, fusée-and-chain, or an extra spiral torsion spring called a remontoire.
Copper (Cu)	An element very often used in the manufacture of watches. Copper is one of the most important materials in watchmaking, especially as a part of an alloy. It is combined with zinc to produce brass, which is used ubiquitously for the crafting of plates and bridges. When combined with beryllium it makes up balance wheels and springs. Combined with tin it becomes bronze, a niche but well-known material for constructing dive watch cases. Copper is an essential ingredient in virtually all types of colored golds, including yellow, red, pink, rose, and even white gold. On its own it serves as the balance of many alloys that dials are made of.
Copper-gilt Dial	A galvanized gilt dial that uses a copper or copper-colored substrate, or a dial that has a similar appearance.
Coral Dial	A dial made of the gemstone coral.
Cornes de Vache	(French) Cow Horns. A style of lugs that resembles cow horns. Also the name of a Vacheron Constantin chronograph with these lugs.
Correct	In watch collecting parlance, a component of a timepiece is said to be ‘correct’ when it is the correct component that belongs on the timepiece but not necessarily original to the timepiece itself. The scope of correctness may vary. To say that a component is ‘period-correct’ is to say that the component belongs to the period of manufacture (e.g. a 1930s handset on a 1930s watch) but not necessarily that it is correct to the exact model (e.g. the aforementioned watch may never have been offered with that handset) or that it is original to the watch (e.g. the handset may be correct in every way but not the original hands installed from the factory). Used most frequently when discussing the components of vintage watches and assessing their authenticity.
Corrector	A mechanical actuator flush to the case which is actuated by being pushed. A corrector is usually in a small round dimple on the case flank. While it can only be actuated with a corrector tool (a small pen-shaped tool with a pin), it has the advantage of being unnoticeable from the front and giving the watch a smoother profile than a protruding pusher. Therefore it is typically used for complications that do not need constant interaction such as dates, calendars, and moon phases.
Corum	A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1955. Corum is owned by the Citychamp Group.
COSC	(French) Contrôle officiel suisse des Chronomètres. ‘Official Swiss Chronometer Testing Institute’. A Swiss organization that certifies the accuracy and precision of watches. In English it is pronounced either [kosk] or read letter-by-letter. COSC-certified watches are said to meet the ‘COSC standard’.
COSC Chronometer	A mechanical or quartz watch that is certified for accuracy by the Official Swiss Chronometer Testing Institute or COSC.
COSC Standard	A set of standards for watch accuracy set by the Official Swiss Chronometer Testing Institute or COSC. COSC maintains different standards for mechanical and quartz watches. Both typically test the watch for around two weeks (13 days for quartz, 15 for mechanical) and check average daily rate of deviation from an atomic time standard, as well as variation in daily rates, accuracy in different positions, and effects of temperature. A watch certified by the COSC standard is called a ‘COSC chronometer’.
Côtes de Genève	(French) Geneva stripes.
Count-up Bezel	A rotating bezel with count-up markings.
Countdown Bezel	A rotating bezel with countdown markings.
Counter Chrono	A nickname for the Seiko reference 5718-8000 chronograph. The nickname is a matter-of-fact description of the watch's complications: a digital lap counter and chronograph.
Counterfeit	An unauthorized copy of an authentic clock, usually a watch.
Coupling Arm Spring	A component of a chronograph mechanism which constantly applies pressure to the coupling arm/lever. This constant pressure which pushes the arm towards the center of the watch where the chrono runner is allows the coupling arm and its wheel to slide towards the chrono runner and start the chronograph. Also called the ‘pivoted detent spring’.
Coupling Clutch/Arm	A component of a chronograph mechanism which moves the coupling clutch wheel bridge and thus is responsible for connecting and disconnecting the driving wheel which provides the energy and the chronograph runner/chronograph wheel which controls the chronograph seconds hand. Mechanically it is equally an arm, a lever, and a clutch, so the three terms may be used interchangeably. As it is also a pivoted detent (referring to its shape as a pivoted lever and its finger which serves as a detent), the arm is also called a ‘chronograph pivoted detent’.
Coupling Wheel	A component of a chronograph mechanism which transfers energy from the driving wheel to the chronograph runner. The coupling wheel is mounted on a pivoting bridge which allows it to make contact (engage) and break contact (disengage) with the chronograph runner.
Coupling Wheel Bridge	A component of a chronograph mechanism which mounts the coupling wheel and is controlled by the coupling clutch. It is screwed onto the coupling clutch and is often simply regarded as a part of it instead of its own component. As it is mounted onto a pivoted detent (referring to its shape as a pivoted lever and its finger which serves as a detent), it is also called a pivoted detent bridge.
Cover Plate	A plate that mounts the intermediate wheel and moves into position to mesh it with the minute wheel. The cover plate is machined with an integrated detent spring which rests on a pin on the setting lever. When the crown stem is pulled into setting position, the setting lever moves, pushing the detent spring and the rest of the cover plate so that the mounted intermediate wheel can mesh with the minute wheel.
CPCP	Collection Privée Cartier Paris. A range of timepieces made by Cartier in 1998 in response to a renewed demand for mechanical timepieces. CPCP watches revived many designs from Cartier’s past and used mechanical calibers instead of quartz modules. The CPCP lasted for about a decade and came to an end in the late 2000s.
Crab Lugs	A style of lugs with an inward curve that resemble crab claws. Also known as ‘crab claw lugs’. Crab lugs are somewhat ill-defined, and spider, teardrop, and horn lugs are often conflated with crab lugs. Generally, crab lugs have a noticeably curved profile unlike the angular profile of spider lugs. Each lug resembles the propodus (the fixed, larger, and curved part) of a crab or lobster’s pincer.
Credor	A brand of high horology watches owned by Seiko.
Cross-threading	A type of engagement failure that occurs when the threadings of the male and female components do not align correctly, typically as a result of incorrect angle of insertion or excessive force. Cross-threading may lead to stripping.
Crosshair Dial	A dial style with a crosshair at its center. The crosshair divides the dial into four quadrants, which is supposed to make the dial more legible. It is also a stylistic choice. Many subdials also utilize the crosshair design. In some instances, the crosshair dial is regarded as a type of sector dial. In the strictest sense, a crosshair dial is divided into quadrants while a sector dial is divided into rings. However, the two are not mutually exclusive and are often combined.
Crow's Foot	See 'broad arrow'.
Crown	A button-shaped knob with a knurled, fluted, or otherwise textured rim that allows the wearer of a clock to interact with the movement without opening the case. The crown is primarily used for setting the time, winding the mainspring, and setting other features in the clock. A crown can be pulled out to various positions to access its different functions.
Crown Gear	A gear with teeth, often saw-teeth, arranged in a ring at a right angle to the face of the wheel and parallel to the axis of rotation. It resembles an archetypal crown. It is similar to the bevel gear, of which it may be considered a type, but the key difference is that a crown gear's pitch cone angle is 90 degrees whereas any other pitch cone angle would make the gear a bevel gear. They are visually very distinct from each other. Moreover, unlike bevel gears which typically mesh with other bevel gears, crown gears usually interact with spur gears or even rods. Crown gears were hugely important in watchmaking during the days of the verge/crown wheel escapement. Today, crown gears are even more ubiquitous as they are essential components of the crown stem assembly which transmits power from the winding stem (a rod) to the wheel train.
Crown Guard	A protrusion from the case which flanks the crown to protect it from external impact. Crown guards usually come in pairs. While the reduction of exposed crown area makes it slightly more difficult to operate the crown, the payoff is that the most vulnerable part of the watch is protected from at least three sides: the rear where the wrist is, and the top and bottom. Crown guards are common on dive watches.
Crown Stem	A stem that is connects the crown and the keyless works of the watch. The crown stem’s primary roles are to wind the mainspring via the winding pinion and set the time via the sliding pinion. Thus, a typical crown stem consists of a threading at one end for the crown, a winding pinion a little further down from the midsection, and a sliding pinion at the other end.
Crown Wheel (component)	A component of the keyless works that connects the crown stem’s winding pinion and the ratchet wheel that sits on the mainspring barrel. The crown wheel can be easily spotted as the smaller toothed wheel that sits next to the ratchet wheel.
Crown Wheel (wheel type)	A type of wheel where the leaves/teeth are parallel to the axis of rotation, as opposed to perpendicular like in most conventional gears. This gives the wheel the appearance of a crown, hence the name. The crown wheel is a crucial component for the crown wheel or verge escapement. It should not be confused with a component of the same name, whose name comes from its relationship with the crown of a watch.
Crown Wheel Escapement	See 'verge escapement'.
Crystal	The transparent material at the frontside of a clock which allows the viewer to read the information on the dial while simultaneously protecting it from the outside. Crystals are usually made of some form of plexiglas, mineral glass, or sapphire.
Crystal Oscillator	An electronic oscillator circuit that uses a piezoelectric crystal as a frequency selective surface. In watchmaking, the oscillator's property as a frequency selective surface allows it to serve as a timekeeping device. Many types of crystals can be used to make these oscillators, but the quartz crystal is by far the most common in watchmaking. The crystal oscillator is the key component of a quartz movement.
Crystal Press	A tool that is designed to press a crystal into a watch case. The press looks like a typical mechanical press with a lever handle and a spring-loaded pressing cylinder with a plastic or hardened rubber pressing surface.
Curb Pin	A pin that holds onto the balance spring and determines its free/effective length. Curb pins usually come in pairs.
Cushion	A piece of watch furniture meant to have a watch strapped around it. Usually made of velvet, silk, satin, or other soft fabrics and sometimes stuffed with plushy material. Some cushions are hard and non-pliable in order to give structure. Similar to a pillow.
Cushion Case	A case shape that is either a square with four convex sides or a round case with an unbroken semicircular line running from the tips of the lugs to the case flank. The first style can be understood as the inverse of a carré galbée case. The second style is basically a round case with beefier round contours on the case flanks. As the two styles are very different despite having the same name, the latter is often also called a turtle case after the famous Seiko Turtle diver.
Cushion Lugs	A style of integrated lugs that comes on a cushion case (second variety in the ‘cushion case’ entry).
Cuvette	The inner cover behind the hinged cover of a pocket watch. In pocket watches the cuvette typically contains information on the watch's movement or technical specifications. In a looser sense 'cuvette' is used to describe any sort of solid metal hinged cover.
Cycloid(al) Profile	A gear tooth profile based on a cycloid as opposed to an involute. A cycloid is a curve generated by rolling a circle across a line. A cycloid tooth profile takes its shape from sections of a hypocycloid and epicycloid, the former being a curve formed by rolling a circle along the inside of a larger circle and the latter being a curve formed by rolling it on the outside. The dedendum of the profile is hypocycloidal while the addendum is epicycloidal. In simple terms, a cycloid tooth looks like a rectangle with a pointy end and can be distinguished by its relatively straight flanks. This is in contrast with the curvy involute tooth. Today, cycloid profile teeth are almost entirely associated with watchmaking as the rest of the world has moved on to involute profiles. Cycloid teeth retain the upper hand as they provide maximum durability, longevity, minimal friction and wear when there is i) no direct lube, ii) tight space, and iii) long maintenance intervals.
Cyclops	Synonymous with 'magnifier'. A term famously used by Rolex.
Daily Beater	See ‘beater watch’.
Damascening	See 'damaskeening'.
Damaskeening	Also spelled 'damascening'. A finishing technique on the movement where radial and/or circular geometric patterns are etched using a rose engine or similar device. It is similar in many ways with 'guilloché', the difference being that the patterns in damaskeened watches are much shallower, often being simply ground and not carved. Whereas guilloché is almost always a radial pattern, damaskeened embellishments are at times whimsical. The term 'damaskeening' originates from the Syrian city of Damascus and their namesake steel famous for its marbled pattern. The term is almost exclusive to American pocket watches.
Damasko	A watch manufacturer established in Barbing, Germany in 1994. Damasko is privately owned.
Dark Lord	A nickname for Heuer Monaco reference 74033N, a blacked-out Monaco with a matte PVD case, black dial, and orange accents.
Dark Nina	A nickname for Universal Genève Compax reference 885103/1 ‘Nina Rindt’ chronograph with a reverse panda dial.
Dart Tooth	Another name for the finger of the chronograph runner.
Darth Tuna	A nickname for the Seiko SBBN011 diver and any other Tuna that is all-black. 'Darth' is a common prefix attached to watches that are predominantly black. It originates from Star Wars lore.
Darth Vader	A nickname for the Omega Seamaster reference 145.0023, a black tungsten version of the reference 145.023 nicknamed the ‘Anakin Skywalker’. The nickname ‘Darth Vader’ is a reference to the black helmet-shaped shell and was dubbed by renowned collector Chuck Maddox alongside the Anakin Skywalker. In Star Wars lore, Darth Vader is the name of Anakin Skywalker after he turned to the Dark Side much like how the ref.145.0023 and the ref.145.023 are essentially the same watch but in opposite colors.
Date Pusher	A pusher on a watch that adjusts the date display.
Dauphine Hands	A style of hands distinguished by a bold triangular profile. Unlike most hour and minute hands the shoulder (widest point) of a dauphine hand is at the mounting point. The hand culminates with radical triangular taper at the tail. The etymology of ‘dauphine’ is uncertain. A dauphine is the crown princess of France and wife to the dauphin. A dauphin is either the crown prince of France or French for dolphin, the former being derivative of the latter. It is possible that dauphine was a misspelling of dauphin as there is a theory that the name comes from how the sleekness of the hands resembles that of a dolphin. Dauphine hands may be lumed or unlumed.
De Bethune	A watch manufacturer established in Sainte-Croix, Switzerland in 2002. De Bethune is privately owned.
Deadbeat Escapement	A variation of the anchor escapement that eliminates its inherent recoil, hence the name 'deadbeat'. Also called the 'Graham escapement' after a clockmaker erroneously believed to be its inventor. The deadbeat escapement addresses recoil by switching the slope direction of the escape wheel teeth. The deadbeat teeth are pointed towards the direction of rotation while the anchor teeth point against it. The teeth face engages with the pallet face and locks instead of recoiling, completely stopping the escape wheel until it is released on one end and pushed with the other pallet. While more accurate than the base anchor escapements, deadbeat escapements were limited by their tighter manufacturing tolerances. Hence they were used for higher grade clocks.
Deadbeat Seconds	A complication that advances the seconds hand once every second instead of multiple times per second. This is achieved through a secondary escapement which releases the seconds hand only once per second instead of allowing it to move at its natural rate as dictated by the balance. Deadbeat seconds is a useful complication for observation and measurement purposes as it makes the distinction between each second much clearer than a movement which moves multiple times per second. With the advent of quartz watches that naturally tick once per second due to their stepping motor, mechanical watches with deadbeat seconds are sometimes mistaken for quartz watches. Nonetheless, the complication is still appreciated within horological circles.
Deep Diver	A subcategory of dive watch that is designed for ultra-deep depths. Typically watches rated to beyond 1000m of water resistance may be called deep divers. In a sense there is no meaningful difference between deep divers and professional divers other than water resistance. However, the deepest-rated divers often boast oversized, often unwearable cases. These are usually technology demonstrators and not meant to be worn by humans but rather strapped to the robot arms of an ultra-deep submersible.
Delta Timezone	Military timezone name for UTC-4.
Deployant Clasp	A single or double-fold clasp. Commonly referred to as a 'deployment' clasp, which is an English translation of the French word 'déployant'. While all folding clasps are also technically deployant clasps, the term usually refers to those on straps, not bracelets. This is because bracelets rarely use anything but folding clasps as a locking mechanism (and are thus considered unextraordinary) whereas they are less common in straps due to the popularity of the classic pin buckle.
Depth Gauge	An instrument that measures depth. It typically relies on water pressure and comes in both mechanical and electronic forms. While they are rare in mechanical watches, certain models feature bourdon tube depth gauges. On the other hand piezoresistive pressure sensors are comparatively common and can be found often on digital dive watches.
Desk Diver	A dive watch or a person who owns a dive watch that never goes diving. A playfully pejorative term, 'desk diver' makes fun of how many of the buyers of capable and purpose-built dive watches rarely take the watch beyond their office desk. Identical in usage with 'mall crawler' in the automotive world.
Destro	(Italian) A nickname for watches that have the crown on the left/nine o'clock position. 'Destro' is Italian for 'right'. The name comes from how these watches are meant to be worn on the right wrist. Other names for these watches include 'LHD', 'lefty', and 'southpaw'.
Detached Escapement	An escapement which is not connected to the balance, allowing it to swing freely. Examples include the lever, detent, and co-axial escapements.
Detent Escapement	An escapement that utilizes a detent in the form of a flat spring to engage the balance wheel and train. The detent escapement uses pallet jewels mounted directly on the roller to both receive impulses from the escape wheel and release it. Once in motion, a swing of the balance knocks a jewel on the detent which flicks it away from the escape wheel tooth it is obstructing. The escape wheel turns, during which a tooth knocks the longer outer pallet on the roller, providing an impulse to keep the balance running. This simple mechanism reduces a great deal of friction by having the balance interact directly with the escape wheel (and the rest of the train) instead of using a mediary like a lever. Thus, it requires less lubrication which is good for long-term accuracy. It is also a detached escapement, allowing the balance to swing freely. However, the detent is also a weakness that makes the system vulnerable to timing errors from shocks, bumps, and vibration, and is not self-starting.
Dial	The plate which forms the background of a clock on which the time and other information may be displayed. The dial is also called the 'face', 'clock face', and 'watch face'.
Dial Diameter	The diameter of a dial or clockface. Watches with small dial diameter compared to case diameter usually wear smaller.
Dial Protector	A plastic sheet that is placed under the hand stack and over the dial so that the hand removal tool does not damage the dial. The protector is typically a rectangular sheet with a slit down the middle so that the cannon pinion can slide through it.
Dial Washer	A bent and tensile ring of metal (copper or brass) which is placed on top of the hour wheel and on the underside of the dial to apply pressure to the hour wheel so that it does not fall out of position. This is because the hour wheel typically sits freely on the cannon pinion.
Diamond Hands	A style of hands distinguished by a thin base leading to a collar and elongated diamond tip. Diamond hands are typically not lumed.
Digital Display	A display which uses numbers to tell the time. Antonymous with 'analog display'.
Digital Watch	A watch with a digital display. Antonymous with 'analog watch'. While digital watches commonly refer to electronic watches which display the time with either an LCD or LED, a mechanical watch can also be digital as long as it shows the time digitally, i.e. with numbers, rather than with hands.
Direct Center Seconds	An arrangement of center seconds where the fourth wheel is at the center of the movement. This allows the seconds hand to be mounted at the center of the movement with no extra gearing. In a typical arrangement, the second wheel which drives the minutes and hours is set off-center to make way for the fourth wheel, instead utilizing intermediate gearing for the hour and minute hands. Direct center seconds architecture has the advantage of a simpler and thinner arrangement than indirect center seconds. However, in its earliest stages it was costly to completely redesign the layout of the movement.
Dirty Harry	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 16753 'Root Beer' worn by Clint Eastwood. The watch is also simply known as the 'Clint Eastwood' but is more commonly called by the catchier 'Dirty Harry' who Eastwood starred as in 1971.
Disco Volante	(Italian) Flying Saucer. In watchmaking, 'Disco Volante' is a nickname given to wide, flat, and thin watches with particularly round profiles. Many of these watches do not have visible lugs, further accentuating the roundness. The name is most associated with the Audemars Piguet reference 5093 and the Patek Philippe reference 2552. It has also been used for the Omega reference CK2013 and the Jaeger-LeCoultre E562. Also see 'soucoupe'.
Display Caseback	See 'exhibition caseback'.
Disposable Watch	A watch that is meant to be disposed of when its battery runs out or the movement malfunctions.
Dive Watch	A category of wristwatch designed to be used underwater by divers. Once essential tools that were crucial for dives, dive watches are now at best backup timers and virtually unnecessary with the advent of dive computers. Nonetheless, dive watches still have strict guidelines governed by standards bodies like ISO and DIN. They are required to have at least 100m of water resistance and must be certified to at least 25% above their claimed water resistance level. In addition they are required to have a function to measure elapsed time, legibility in the dark, resistance to magnetism and salinity, among others. Dive watches are popular due to their distinct design, practicality, and durability. They are also called ‘divers’.
Diver	See 'dive watch'. In watchmaking a diver may refer to both a person who dives and a watch that is designed to be taken diving.
Diver Hands	A style of hands that is mounted onto dive watches. Diver hands can come in a wide array of styles which all commonly have very broad surfaces to accommodate lume. Diver hands must be lumed.
Doctor's/Nurse's/Medical Watch	A category of wristwatch designed for medical professionals. Medical watches are almost always equipped with a pulsometer and/or asthmometer scale. Sophisticated watches often have chronograph complications to complement the medical scales. These are usually called 'doctor's watches'. The more accessible 'nurse's watches' have a modified seconds hand and/or two of the same scale printed on opposite ends of the dial to make up for the lack of a controllable seconds hand. Both doctor's and nurse's watches have clean, legible white dials.
Doppel	Short for ‘doppelchronograph’, German for ‘split-seconds chronograph’.
Doppelchronograph	(German) Double chronograph. Synonymous with ‘split-seconds chronograph’.
Doppelfederhaus	(German) Double barrel. Literally means 'double feather (spring) house', referring to the two spring housings or barrels. Also see 'double barrel'.
Dot Matrix Display	A system of displaying information such as numbers, letters, and symbols by selectively showing dots or pixels. Dot matrix displays are capable of displaying more complex shapes than seven-segment displays and may be able to emulate them if the dot matrix is of sufficiently high resolution. Many digital watches use both the dot matrix and seven-segment displays for different types of information or as a matter of style. Also see ‘seven-segment display’.
Dot-Over-Ninety (DO90/DON)	‘Dot-over-ninety’ describes a configuration of the Speedmaster tachymeter bezel where the dot marker for 90 is above the number. If not over 90, it is located next to it at the superscript position (90^). While it is a minute detail, a DO90 bezel is characteristic of Speedmasters produced before 1970 and can serve as a key detail in confirming the authenticity of the bezel. Certain modern reissues of pre-1970 Speedmasters convey this characteristic.
Double Barrel	A mechanical movement with two barrels means that it can store more potential energy than a typical movement with one barrel. Most double barrels are wound simultaneously by the crown, but some are wound separately with counterclockwise and clockwise crown rotation.
Double Eagle	A nickname for models of the Omega Constellation family with two griffes, or claws, on each side of the bezel. The name is a reference to the golf score ‘double eagle’ (American golf terminology for Albatross).
Double Red Sea-Dweller (DRSD)	A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 1665 with 'Sea-Dweller' and 'Submariner 2000' in red ink. The Double Red ref.1665 was produced for about a decade until the 'Submariner 2000' line was dropped.
Double Roller Escapement	An escapement which utilizes a two rollers, with a ‘safety roller’ stacked on the main roller. A double roller setup divides the roles of a single roller to two rollers. The ‘impulse roller’ serves as the standard roller, hosting the impulse jewel and knocking the pallet fork. The ‘safety roller’ is a smaller-diameter roller stacked below the larger impulse roller and is designed to engage with the guard dart in the event of a strong impact that could throw the escapement off alignment. The smaller diameter of the safety roller allows it to engage the guard dart more efficiently in the event of impact. A double roller can be identified by the lack of a passing hollow cutout on the rim of the main roller table as the passing hollow is on the safety roller underneath.
Double Split Chronograph	A variation of the split-seconds chronograph which is capable of splitting the minutes as well as the seconds. Unlike the regular split-seconds chronograph which can only record the difference in two time intervals in seconds, the double split chronograph has a splitting chronograph minute hand which records the elapsed minutes of the split. As the split-seconds chronograph is already an immensely complex complication, the double split is multitudes more difficult to engineer. There is also a triple split chronograph which can split the hours as well.
Double Swiss	A Rolex dial with two ‘Swiss’ origin markings, one in the older position outside of the minute track and the other stamped again between the six o’clock marker and chapter ring, where it remains to this day. The Double Swiss stamping is a result of the introduction of the Daytona, which featured a wider bezel than other models (thanks to its tachymeter) that partially covered the original Swiss marking. This led Rolex to double stamp in the new position to ensure visibility. However, other models including the Submariner, Explorer, and GMT-Master may also feature a Double Swiss dial.
Double Wristing	The act of wearing at least one watch on each wrist.
Double-fold Clasp	A clasp that opens from two ends. Also known as a butterfly clasp.
Double-signed	In watch collecting parlance, 'double-signed' can mean two things. It can mean that a watch is signed with the manufacturer's name in two places, usually the dial and movement. This use is more common when discussing pocket watches. The more common definition means that the watch bears two different signatures on the dial, usually by the manufacturer and retailer. Double-signing is a rare occurrence these days and retailer signatures from certain reputed jewelers and watch sellers may command high prices. Also see 'retailer signature' and 'triple-signed'.
Dress Watch	A category of wristwatch distinguished by its classical and conservative form factor. Some define the dress watch as a watch designed to be worn with formal dress, which may also be an appropriate definition. Pinpointing the exact parameters of a dress watch is quite difficult as the dress watch is the quintessential and oldest style of wristwatch, dating back to an era when even military uniforms were formal by the standards of today. The dress watch is defined purely by aesthetic instead of function, and especially pertains to the case profile and somewhat less to the dial features. Generally it is agreed that a dress watch case prefers simple and elegant lines and surfaces with minimal protrusions such as pushers, crown guards, or ears. They are meant to be unobtrusive and subtle, usually coming in a smaller case size and a leather strap which minimize the presence of the watch and allow it to slide under a dress cuff. Nonetheless, any watch can be a dress watch as long as it looks 'dressy'.
DRIE	Deep Reactive Iron Etching. A manufacturing process that is used to manufacture small components out of silicon wafers with high precision through lithography and plasma etching.
Drift	The deviation in a clock's accuracy, particularly in the context of quartz movements.
Drilled Lug	A type of lug whose spring bar hole is drilled all the way through the lug. Drilled lugs can be identified by the holes on the outer faces. The outer holes make spring bar removal much easier as a simple poke of a spring bar tool through the hole is enough to depress the spring bar head.
Driving Hook	A hook which grabs a tooth on the side of the rack and drives it to make a sound. Which tooth the hook latches onto determines the number of chimes as it dictates how many teeth on the bottom of the rack pass through the hammer trip.
Driving Watch	A category of wristwatch designed for driving. Driving watches were particularly popular in the 1970s as quartz watches with sideways digital displays. Today the category encompasses watches that pay tribute to automotive culture and those inspired by automobiles. While it is a relatively niche genre, the large overlap between watch and car enthusiasts makes the driving watch a cult favorite.
Driving/Transmission Wheel	A component of a chronograph mechanism which is co-axially mounted with the fourth wheel of the movement via an extended pivot.
Dropshipping	The practice of selling products that the seller does not physically have in stock, instead putting in the order on the buyer’s behalf to the manufacturer which the seller typically has no affiliation with. In the watch world, the term specifically refers to the practice of ordering generic unbranded watches from (usually overseas) factories, applying a company logo, and selling them to consumers. As the seller running the brand has little if any involvement with design, production, and distribution, the seller is occupied entirely with marketing. Dropshipped watches typically rely on exaggerated marketing and deceitful brand image building to sell cheap watches for multiple times their original price from the factory and target the non-enthusiast public.
Dual Time Complication	A complication that displays another timezone. The terminology is vague, as it technically includes the more specific and better-known GMT complication. In common usage, a dual time complication is one that displays both the hours and minutes of the second time zone. The minute hand on the second time zone subdial is usually synchronized to the regular minute hand. When it is not, a dual time complication becomes capable of displaying timezones offset in sub-hour increments such as Indian Standard Time. As the second time zone hour hand is typically a 12-hour hand, dual time watches come with day/night or am/pm indicators.
Dust Blower	A handheld silicone or rubber air blower that is used to blow dust and lint off a movement.
Dust Resistance	A timepiece's ability to stop dust from entering the case. Dust resistance was a concern during the times when the internals of the watch were frequently exposed, such as open face pocket watches and holes for winding and setting keys. Today, dust resistance is not as much of a concern as watches are almost completely sealed off. Thus it is rarely mentioned.
Eastern Arabic Numerals	A type of numerals featured on watch dials, also called Mashriki numerals or Indo-Arabic (ʾarqām hindiyyah) numerals. They are genetically related to the more famous western Arabic/Ghūbar numerals, both having descended from the Hindu number system. While western Arabic numerals gained international use after further evolution in medieval Europe, eastern Arabic numerals remained contained to the eastern Arab world or 'Mashriq', hence the name. In watchmaking eastern Arabic numerals are considered a novelty or a region-specific feature.
Easylink	A quick adjustment extension system mounted onto certain Rolex Oyster and Jubilee bracelets. Easylink utilizes folded half-links towards the anchor which can be unfolded to give 5mm of extra bracelet length. This simple system is Rolex’s most widespread quick extension system due to its compactness.
Ébauche	(French) Literally means blank, sketch, or outline. In watchmaking the term refers to a usually incomplete and/or unassembled watch movement that is sold to other companies which will assemble and/or complete the movement and put it in a watch. In the past, ébauches included plates, bridges, gear train, and winding mechanism but not the escapement, balance, or mainspring. Today, the term is used more loosely and refers to any blank movement that is meant to be modified, regulated, branded, and fitted to a watch by another watch brand, regardless of the completeness of its components. See 'third party movement', 'in-house movement', and 'proprietary movement' for comparison.
Eccentric	In mechanical engineering, an eccentric is a disk that is fixed to an off-center rotating axle. In watchmaking, especially in chronographs, ‘eccentric’ refers to an ‘eccentric stud/screw’. See ‘eccentric stud/screw’.
Eccentric Stud/Screw	A component of a chronograph mechanism which is a screw-headed stud that fastens several important levers of the chronograph. They are more commonly referred to as ‘eccentrics’. These studs can be adjusted to finely tune the operation of the chronograph and may cause severe friction and wear if poorly fiddled with.
Echo Timezone	Military timezone name for UTC-5.
Eco-Drive	A brand of light-powered quartz movement produced by Citizen.
Ed White	A nickname for the Omega Speedmaster reference 105.003 and its modern descendant the reference 311.30.40.30.01.001. The ref.105.003 is named after American astronaut Edward White II, who wore two of these watches on the first American extravehicular activity, or spacewalk, in 1965. The ref.105.003 was the first Speedmaster to be approved by NASA by for all manned space missions and introduced the baton hands that would become standard for all subsequent Speedmasters. The 2020 ref.311.30.40.30.01.001 which heavily references the ref.105.003 and carries the same cal.321 movement is also called the Ed White.
El Cornino	(Spanish) A nickname for the early examples of the Rolex Oyster Perpetual GMT-Master 1675 featuring pointy crown guards (PCGs). The name is a reference to how the PCGs look like horns. Also see ‘PCG’.
Electric Movement	A type of hybrid movement which existed primarily in the 1950s and 1960s. Electric movements utilize the electric current from a battery to power the action of a traditional balance spring or a tuning fork which vibrates upon receiving a charge. Electric watches were rendered obsolete by the introduction of purely electronic watches which utilized quartz crystal timing packages which were far more accurate.
Electronic Movement	One of the three major types of movements. Electronic movements use an electrical power source such as a battery or capacitor to power an electronic timekeeping device like an integrated circuit/microchip. Virtually all electronic movements are quartz movements which use a quartz crystal to serve as a timing reference. Thus, the term 'quartz movement' is a far more widely used and recognized term.
Émail	(French) Enamel.
EMRO	Émeraude. Rolex nomenclature for a bezel set with baguette cut emeralds.
Enamel	A glassy coating baked onto ceramic or metal surfaces. Enamel can be both a decorative and practical technique. In watchmaking, enameling is widely used on dials for decorative effect. The most common variety is vitreous enamel which can be applied to various techniques such as cloisonné, flinqué, and champlevé.
End Link	Links (metal components of a bracelet) that connect the rest of the bracelet to the watch head. End links may be a single component or may consist of several interlocking components. Not all bracelets have end links and some straps have end links. End links allow for a seamless connection between the head and band. Also see 'solid end link' and 'hollow end link'.
End of Days	A nickname for the Audemars Piguet Royal Oak Offshore reference 25770SN. The watch was designed with input from bodybuilder, actor, and former governor of California Arnold Schwarzenegger as he was to wear it in the 1999 film End of Days.
Endshake	The vertical tolerances of a jewel. An example of endshake would be the travel distance of a pivot in relation to the jewel it makes contact with. Appropriate levels of endshake are necessary for watch parts to move properly, minimize friction, and/or absorb shocks. Excessive endshake may result in disengagement of a watch component with its jewel. Insufficient endshake may slow down or seize the watch by causing excessive friction. Also see ‘sideshake’.
Engine	Short for 'rose engine lathe'.
English Lever Escapement	A now-obsolete style of the lever escapement. The balance wheel and lever form one axis that is perpendicular with that of the escape wheel. In the English lever escapement, the lever is I-shaped, with one end of the I flat and the other having a swallowtail cut to engage the impulse pin on the balance wheel. The two pallets are mounted on one side of the I. The escape wheel teeth are different as well, as English escape wheels have sloped spike teeth. While the lever escapement is an English invention, the Swiss lever escapement eventually replaced it in virtually all mechanical movements.
Enhanced Grain Leather	A type of leather. It refers to top grain leather from the top of the animal's hide that has been treated for imperfections and blemishes and stamped with an artificial grain print.
Enicar	A de facto defunct watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1914. Enicar was declared insolvent in 1987 and its assets and name were sold to different companies. The name is owned by Wah Ming Hong Ltd.
Entry Pallet	A pallet jewel on one end of the pallet fork which is the first to contact an escape wheel tooth. The entry pallet is typically mounted on a shorter arm and is angled more gently than the exit pallet.
EOL	‘End of Life’. An EOL indicator is a feature on a quartz timepiece which signals that the battery is at the end of its life. Whereas mechanical timepieces can simply be wound to replenish the power reserve, quartz timepieces cannot function at all without a battery. Hence, an EOL indicator is an important feature for quartz watches. In digital watches with LCD/LED display, an EOL icon will appear. In analog watches, the seconds hand typically leaps two hash marks every two seconds (instead of one every second) to get the owner’s attention. EOL indicators are mandatory for quartz dive watches.
Equation of Time	The difference between apparent solar time and mean solar time. Apparent solar time is based on the actual movement of the sun, which varies because of Earth’s elliptical orbit and tilted axis of rotation. Mean solar time is time that is kept by humans based on the assumption that each day is exactly twenty-four hours long. Also see ‘apparent solar time’, ‘mean solar time’, and ‘equation of time (complication)’.
Equation of Time (complication)	An astronomical complication that indicates the equation of time. It is usually a circular sector with a hand that indicates the equation of time between +15 and -15 minutes on a scale.
Escape Wheel	A component of the going train that is the fifth and final wheel to transfer energy from the unwinding of the mainspring. It is also a component of the escapement. The escape wheel interacts with the fourth wheel pinion and knocks the pallet fork, which knocks the balance wheel via the impulse jewel. The escape wheel is designed so that it interacts with the pallet fork to seize the going train until the impulse pin comes back to strike the pallet fork and free the escape wheel, allowing the movement to advance. This continuous cycle of seizing and releasing the going train is what determines the speed of the movement. To fulfill this role, the escape wheel is markedly different from the other wheels of the going train as it has heavily slanted club-footed teeth.
Escapement	In a general sense, an escapement is a mechanism that regulates the motion of other components, typically by locking and releasing a moving part. In watchmaking, an escapement is a mechanical linkage that regulates the motion of the gear train at a speed determined by the timekeeping mechanism. Escapements have existed in various forms throughout history, with fluid-driven escapements likely acting as the first reliable systems until verge escapements appeared in 13th century Europe.
Établissage	(French) A general term for the manufacturing process of a timepiece from readymade components, specifically concerning how an ébauche and unassembled components are received, assembled, tested and timed, cased, and dispatched. ‘Établissage’ is French for ‘workbench’.
Établisseur	(French) A factory or individual who buys components from suppliers, usually to assemble but sometimes also to finish or modify. An établisseur may outsource the actual terminage work (assembling the watch) to an atelier de terminage.
Eterna	A watch manufacturer established in Grenchen, Switzerland in 1856. Eterna is owned by the Citychamp Group.
Etoqueau	(French) A Genevan French term for a banking pin. See ‘banking pin’.
Exclamation Point Dial	A nickname for radium Rolex dials of the early 60s (mostly 1962) which feature a dot on the minute hash below the six o’clock baton marker, making the pair look like an exclamation point. This is an indication that the watch is compliant with then-new radiation regulations from the Atomic Energy Commission, and features less radium than before. Rolex’s radium dials ceased production in 1963, which ushered in the transitional tritium conversion dials. Also see ‘underline dial’ and ‘T < 25’.
Exhibition Caseback	A caseback that has a crystal window that provides a view of the movement. Also known as a clear caseback or sapphire caseback.
Exit Pallet	A pallet jewel on one end of the pallet fork which is the second to contact an escape wheel tooth. The exit pallet is typically mounted on a longer arm and is angled more steeply than the entry pallet.
Exotic Dial	A variation of a dial that is usually rarer, quirkier, and/or more experimental than the main variant. The most famous exotic dial is perhaps the one mounted on the Rolex Cosmograph Daytona reference 6239, which would later be called the ‘Paul Newman’ dial.
Exotic Nina	A nickname for Universal Genève Compax references 885107 and 885108 ‘Nina Rindt’ chronographs with exotic dials.
Expansion Bracelet	A bracelet that can be stretched. Some expansion bracelets stretch only a modest amount while others can contort like a slinky. Also see 'rivet bracelet' and 'Twist-o-flex'.
Expedition/Exploration Watch	A category of wristwatch designed for expedition, exploration, and adventure on land. The category is somewhat vague but it includes famous types of watches like mountaineering/alpinist watches, spelunking/cave exploration watches, and expedition watches. They can be understood as the civilian counterpart to the famous field watch. Generally these watches have high visibility at night, shock and water resistance, and often have tools useful for navigation like a compass, altimeter, or barometer.
Extra	See 'oversize(d) watch'.
Extract	Short for ‘extract from the archives’.
Extract from the Archives	A document detailing the date, location, and other details of a timepiece’s manufacture and retail issued by the original manufacturer of a timepiece at the request of an individual. This document usually applies to older timepieces and can serve as an important piece of paperwork for vintage watches whose original documentation is usually lost. Extracts are not certificates of authenticity because obtaining an extract rarely requires more than photos and movement/case serial numbers. However, an extract will at least demonstrate that the serial number of a movement is valid. Information on certain extracts will allow the recipient to discern modifications done on their watch. Therefore, while an extract is not a suitable proof of a watch’s authenticity, it is still good to have. It should be noted that most manufacturers do not provide this service.
F. P. Journe	A watch manufacturer established in Geneva, Switzerland in 1999. Abbreviated ‘FPJ’. F. P. Journe is privately owned.
Fab. Suisse	(French) Short for 'Fabriqué en Suisse'. Means 'Made in Switzerland'. Also see 'Swiss Made'.
Fabric Strap	A strap that is made of fabric such as nylon, canvas, sailcloth, cotton, etc. Composed of either one piece or two pieces.
Face	Synonymous with ‘dial’.
Faceted Lugs	A style of lugs, usually tapered, distinguished by flat faceted surfaces instead of curved ones. Whereas the top side of a tapered lug gently curves downwards to the tip, faceted lugs replace the curve with two or three flat surfaces. This style of lugs was famously used in many cases made by Spillmann & Co. which supplied cases to numerous named brands in the mid-20th century. Hence, these lugs are sometimes called ‘Spillmann lugs’.
Factory	When something is described as 'factory' in watchmaking, it means that it is the way it came from the factory, without modifications done by a third party. A comparable term is 'stock' in the automotive world. The term is especially used to describe interesting, quirky, or rare features of a watch that are worth mentioning such as gem settings, unique colors, or engravings that were approved and executed by the original manufacturer of the watch. It is antonymous with 'aftermarket'.
Fagiolino	(Italian) Little bean. A style of lugs that have a curved oblong profile reminiscent of a bean. The name likely arose from the lugs of the Patek Philippe reference 591.
Fancy Lugs	A catchall term for flamboyant and unconventional lugs styles.
Fashion Watch	A term, often derogatory, for a watch that is either (i) sold under a fashion brand, or (ii) made by a brand whose watches focus more on generically popular designs than watchmaking. While the term is broad, it usually refers to cheap watches that are produced for retail at high markup by famous brands typically to the general public and not watch enthusiasts. Some more extreme uses of the term include some watches produced by brands that don’t focus solely on watches such as jewelry brand Cartier and fashion brand Hermes.
Fat Lady	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 16760, a GMT-Master II with a black and red aluminum bezel and red GMT hand. The name 'Fat Lady' is a reference to the beefy case that was needed to accommodate the upgraded movement, which was the first iteration of the GMT-Master II that could display one more timezone than the GMT-Master and had an independently-adjustable hour hand. The watch was also dubbed the 'Sophia Loren' for the same reason and the 'Coke' for its colors.
Faux	(French) Fake. In watchmaking the term typically describes non-functioning or unoriginal components that exist purely for cosmetic appearance. They are particularly common in watches that reference vintage designs.
Faux Rivets	Metal rivet heads attached to the side of an outer link to mimic the appearance of a riveted bracelet.
Fauxtina	A surface treatment or color that is meant to simulate patination. A portmanteau of the French word 'faux' (fake) and 'patina', sometimes used in a derogatory fashion. Fauxtina is especially popular for lume plots as the creamy yellowish lume of vintage watches is desirable.
Feeler/Finger	The hooked end of a rack in a repeater. The feeler interacts with the levels/steps on the snail cam.
Feiko	Watch collecting slang for a fake Seiko watch.
Feuille Hands	See ‘leaf hands’.
Field Watch	A category of wristwatch designed to be used by soldiers fighting on land. Field watches were arguably the first men's wristwatches as they were born out of a need to keep a timepiece on the wrist instead of the pocket during the wars of the 19th century. The field watch as we understand it today is largely based on designs from the 1950s to 1970s when wristwatches with highly legible dials, rugged reliability, and cheap cost of manufacture were standardized, ordered, and issued by the militaries of the world. However there is still variety within the field watch category, such as the classic trench watch, officer's chronograph, and digital field watch.
File	A tool with an abrasive surface that is used for filing down surfaces.
Fils Hands	See ‘baton hands’.
Finger	A particularly long leaf or protrusion, especially on a wheel or pinion. Fingers are useful for transforming continuous movement to periodic movement.
Finger Condom	See 'finger cot'.
Finger Cot	A latex or rubber cover worn over one or more fingertips to prevent contamination. In watchmaking, finger cots are useful for watchmakers whose dexterity may be negatively affected by a full latex glove or when only a select few fingers need be covered. Finger cots prevent natural oils produced by the human body as well as other contaminants carried by the hands from coming into contact with surfaces on a watch, especially the movement. They are more commonly known as 'finger condoms'.
Finish	The manner in which a surface has been finally treated. Finishes can be done for both practical and aesthetic purposes.
First Wheel	A component of the going train that is the first wheel to transfer energy from the unwinding mainspring to the rest of the motion works. The first wheel is in fact the mainspring barrel itself, as the barrel is lined with teeth that make it a wheel. It is also known as the ‘great wheel’.
Five-minute Repeater	A striking complication that repeats (chimes) the hours and every five minute interval that has elapsed since the last hour. Typically the hours are sounded with a bass note and the five minute sections with a treble note or one of each.
Fixed Bar	A type of bar that is permanently fixed in position. Fixed bars may either be designed as such or soldered on later. They resolve the small but extant failure risk that spring bars have. The tradeoff of fixed bars is that they can only receive one-piece straps such as natos and zulus or antiquated leather straps that loop around the bars. Fixed bars are commonly found on military watches.
Flame Lugs	A style of lugs that resemble a flame. The term is somewhat broad, but a flame lug generally resembles a curved twisted lug with additional decorative bolstering on the outer side.
Flashing Seconds	See ‘foudroyante seconds’.
Flat Four	A nickname for a variant of the Rolex Oyster Perpetual Submariner 16610LV ‘Kermit’ which features a noticeably flat and wide top on the number ‘4’ in 40-minute marker of the rotating bezel. Perhaps the best-known variant of the Kermit, the Flat Four is a distinguishing mark of the first series of Kermits produced. Because the Kermit is a 50th anniversary model for the Rolex Submariner, the Flat Four is regarded as the ‘true’ anniversary model as it was released in the actual anniversary year.
Flat Four Sans-serif	The later variation of the Rolex Kermit Flat Four which does not feature any serifs on the bezel numerals. The Sans-serif font itself would become standard for all later iterations of the Kermit.
Flat Four Serif	The earlier variation of the Rolex Kermit Flat Four which features small serifs on the bezel numerals. The Serif was soon replaced by the Sans-serif or Non-serif Flat Four.
Flat Link Bracelet	A three-link bracelet with wide center links, narrow outer links, all with a very short and completely flat profile. Flat link bracelets were made by Omega for the Omega Speedmaster.
Flatback	A nickname for Rolex Bubbleback-style Oyster Perpetuals that were offered with a manually-wound movement. The lack of an automatic winding mechanism eliminated the need for the bulbous caseback which gave the Bubbleback its nickname. Hence, these watches were called Flatbacks.
Flecto	Watch collecting social media lingo for the reflections on a watch crystal. Different crystal materials and shapes produce vastly different types of reflections.
Fleur-de-lis Hands	A style of hands distinguished by fleur-de-lis-shaped tips. Fleur-de-lis hands are not lumed.
Flighty	A nickname for the Seiko Flightmaster family.
Flinqué	(French) A decorative technique where vitreous enamel is poured onto a guilloched/engine turned surface, usually a dial. The vitreous enamel pools in the grooves of the engine turned dial, resulting in a beautiful end product where the engine turned surface is visible under a translucent layer of glassy enamel. Flinqué is highly desriable because it marries two highly respected techniques and because faulty dials cannot be corrected, only remade from scratch.
Flip	The act of selling a watch that was purchased purely for the expectation of selling at profit rather than personal use. Flipping is done with watches that trade at or are expected to trade at a value that exceeds the MSRP. A person who flips watches is called a ‘flipper’.
Fliplock	A quick adjustment extension system mounted onto certain Rolex Oyster bracelets. Fliplock utilizes foldedn links towards the anchor which can be unfolded to give 26mm of extra bracelet length. Fliplocks are usually paired with Glidelocks to provide maximum extension on heavy duty dive watches which need to fit over thick diving suits.
Flipper	A person who routinely flips watches for profit.
Flirt	See 'surprise piece actuating lever'.
Flyback	A mechanism which rapidly resets a hand to its default position without having to stop it first. Also see ‘flyback chronograph’.
Flyback Chronograph	A chronograph that is capable of resetting to zero without first stopping. In a normal chronograph, pressing the reset pusher while the chronograph is still in operation will do nothing or damage the movement. A flyback chronograph will always reset the chronograph at any time, regardless of whether the chronograph mechanism is in use. This allows the flyback chronograph to time two consecutive and separate events without delay. Additionally, the flyback mechanism makes the chronograph virtually ‘unbreakable’ as the pushers can be pushed in any order whatsoever with no damage to the movement.
Flyback Lever	A component of a chronograph mechanism which allows a flyback chronograph to reset the chronograph without first stopping it. Essentially, the flyback chronograph combines the stopping, resetting, and starting procedures into one and this is made possible by the flyback lever. The lever is connected to the reset lever and the coupling wheel bridge/clutch bridge or the coupling arm. Pushing the reset pusher moves the reset lever, which pushes the flyback lever via a stud or some other form of contact which in turn pushes away the clutch wheel from the chrono runner. This decouples the chronograph mechanism from the movement’s power delivery (stop) and allows the reset hammers to knock the chronograph wheels back to zero (reset). Finally, releasing the reset pusher recouples the clutch, resuming power delivery to the now-reset chronograph runner (start).
Flyback Reset Lever	A component of a chronograph mechanism which is a slightly modified reset lever to fit the functionality of a flyback chronograph. Unlike a regular reset lever, the flyback reset lever does not have a finger or beak that pushes against the wall of a column wheel pillar. In a normal chronograph this finger is a safety feature that prevents the reset lever from activating when the chronograph is running. This is obviously not needed in a flyback. Another modification is the addition of a stud which pushes the flyback lever.
FOIS	A nickname for the Omega Speedmaster reference 2998 and the various watches inspired by it since 2012. The nickname FOIS which stands for ‘First Omega in Space’ comes from the fact that the ref.2998 was worn by American astronaut Walter Schirra during the 1962 Sigma 7 mission, making it the first Omega watch to leave Earth. It is also called the ‘Wally Schirra’ in honor of the man himself. Various modern Speedmasters that reference the aesthetics of the ref.2998 are dubbed FOIS as well. They share alpha hands, symmetrical case, smaller size, applied logo, and other details that do not exist in the modern Moonwatch which is largely based on the aesthetics established in ref.105.012.
Fork Horn	A horn at the fork end of the pallet fork. A pallet fork has two fork horns and usually a guard dart attached between the two horns.
Foudroyante	(French) Lightning. In watchmaking, the term refers to foudroyonte seconds. See ‘foudroyante seconds’.
Foudroyante Seconds	A complication wherein the seconds hand is engineered to display fractions of a second through a hand that completes a full rotation every second instead of every minute. Technically, any mechanical watch inherently shows fractions of seconds because it beats several times (usually between 5 to 10) a second. However, these fractions cannot be read because they occupy a microscopic segment of the seconds track. A foudroyante seconds makes these fractions more legible by having a dedicated seconds subdial with a seconds hand that makes a full rotation every second. For example, for a watch that beats 10 times a second, each tenth of a second would be allocated 0.6 degrees on a conventional dial whereas it would get 36 degrees on a foudroyante seconds subdial. Having such a short rotation cycle means that the foudroyante seconds hand jumps around the subdial at lightning-fast speeds, having to cover multiple times the distance a normal seconds hand would. ‘Foudroyante’ is French for lightning.
Fourth Wheel	A component of the going train that is the fourth wheel to transfer energy from the unwinding of the mainspring. A coaxial pinion meshes with the third wheel, turning the fourth wheel once every minute. Therefore the fourth wheel mounts the second hand. In many modern center-seconds movements, the fourth wheel is moved to the center of the movement so that the seconds can be displayed at the center of the dial. In this case, the fourth wheel becomes the center wheel instead of the usual second wheel. On the other end, the fourth wheel interacts with the escape wheel.
Foxtrot Timezone	Military timezone name for UTC-6.
François-Paul Journe	(1957-) A watchmaker hailing from Marseille, France and based in Geneva, Switzerland. François-Paul Journe is the mastermind behind watch manufacturer F. P. Journe.
Franken	See 'frankenwatch'.
Frankenwatch	A clock which contains parts from many donor clocks which are usually not period correct or even from the same manufacturer. Also called a 'franken'.
Fratello	An online watch publication based out of the Hague, the Netherlands.
Freccione	(Italian) Large arrow. A nickname for the Rolex Oyster Perpetual Explorer-II reference 1655, whose large orange 24-hour hand resembles an arrow. It is the less popular but far more accurate nickname than 'Steve McQueen', which the ref.1655 is more commonly called.
Free Sprung	See 'free sprung balance'.
Free-sprung Balance	A balance that does not have a dedicated regulator to adjust the free length of the balance spring. A free-sprung balance has a fixed hairspring length and is instead adjusted by moving the timing screws, inertia weights, or other components on the balance wheel. Free-sprung balances are usually more finely adjusted from the factory and eliminate the variable of spring length. They are thus less susceptible to changes in adjustments by shocks and are more accurate when adjusted correctly. However, they are more complicated to work with than an index-adjusted balance.
Frequency	In watchmaking, frequency is the number of actions a timekeeping organ performs over a fixed period of time. It can be used to describe the frequency of any movement type including both mechanical and quartz. Units of frequency can be Hertz (Hz), beats per second/minute/hour (bps/m/h), or vibrations per second/minute/hour (vps/m/h). Also see ‘beat rate’ for a frequency measurement specific to mechanical balances.
Frequency Reference	An object that moves at a constant and reliable frequency that functions as a reference for timekeeping. A frequency reference is necessary for any timepiece that functions independently of environmental factors like the sun (for sundials). Examples of a frequency reference include pendulums, balance wheels, tuning forks, quartz crystals, an cesium atoms. Also see ‘timekeeping organ’.
Friction Ball	A squishy rubber ball that is designed to open casebacks, especially screw-down casebacks. The friction ball is an excellent way of opening screw-down casebacks without scratching or chipping the caseback, and is sufficient for most casebacks unless they are firmly tightened.
Friction Bezel	A rotating bezel that has a smooth action with no discernible steps or clicks. Friction bezels are fitted on top of a wave spring, a circular flat spring with wave-like bends that give it the properties of a spring. The wave spring's purpose is to provide some amount of resistance so that the bezel does not spin whenever the watch is moved. Friction bezels have the advantage of being able to stop anywhere. Also see 'click bezel'.
Friction Clasp	A clasp that uses sheer friction between its components to lock. As they have no button or latch to release the locked hinge, the wearer must pull the clasp open by force. Friction clasps are generally thinner in profile, simpler, and some would say more reliable than push button clasps.
FS	‘For Sale’. Watch collecting social media abbreviation to indicate that a watch is available for purchase. Also see ‘NFS’.
Fuchsia	A nickname for the Rolex Oyster Perpetual GMT-Master reference 1675 with a distinctly faded and discolored aluminum bezel where the red turns into a pinkish fuchsia. Fuchsias are highly desirable for their beautiful discolorations and were only made for a short period of time before Rolex changed their paint to a more resilient one. Hence, many Fuchsias are faked or bezel-swapped. Particularly pink Fuchsias are also called ‘Pink Panthers’.
Fugu	(Japanese) Pufferfish. A nickname for the Citizen NY0XXX series divers, named so for their spiky bezel that resembles a pufferfish.
Fujitsubo (Citizen)	(Japanese) Barnacle. A nickname for the Citizen 62-6198 Challenge Diver and its modern reissues of the Promaster NB6021 series. The nickname comes from a 62-6198 found washed up on a beach in 1983 after being thrown around the ocean floor long enough for barnacles to engulf the watch. The watch was still running when it was discovered. Also see 'Fujitsubo (Seiko)'.
Fujitsubo (Seiko)	(Japanese) Barnacle. A nickname for all Seiko watches with a fujitsubo/helmet-style case, an oblong-profile case with integrated sloping lug hoods. This includes the Seiko 6139-710X series automatic chronographs and the Seiko 5 Sports Speed-Timer reference 6138-0020 automatic chronograph. Also see 'Fujitsubo (Citizen)'.
Full Grain Leather	A type of leather. Full grain leather is generally regarded as the highest grade of leather. It comes from the very top of the animal's hide. As the name implies, it retains the characteristics of the leather intact. It is very durable and long-lasting.
Full Set	The state of having all the furniture, documentation, accessories, and extra parts that came with the watch upon initial delivery. In addition to box and papers this includes extra bracelet links if any, warranty card if any, hang tags if any, and tools and loupes if any.
Fuseaux Hands	See ‘diamond hands’. ‘Fuseaux’ is French for ‘spindle’.
Fusée	(French) A conical pulley with helical grooves that accommodate a chain which is connected to the mainspring barrel. The fusée is mounted on an output gear through which it transfers energy from the mainspring to the going train with minimal variation. Also see 'fusée-and-chain' and 'constant force mechanism'.
Fusée-and-chain	A mechanism consisting of a fusée and mainspring connected by a roller chain which evens the force output of an unwinding mainspring and delivers even force to the wheel train. The fusée-and-chain is a constant force mechanism that replaced the stackfreed. The unwinding mainspring turns its barrel housing which pulls on the chain, unwinding it from the helically-grooved conical fusée which spins and activates the wheel train via a toothed wheel fixed on top of it. The exact profile of the fusée is engineered to the mechanical properties of the mainspring, but all fusées are narrower at the top as the mainspring barrel will pull with the most torque when the mainspring is fully wound. The increasing diameter of the fusée as the chain unravels makes the resistance correspond to the torque of the mainspring. When the mainspring is at minimal torque, the fusée’s diameter is at its widest, its resistance at its smallest. The fusée-and-chain was mostly replaced by the toothed mainspring barrel by Lépine.
G-SHOCK	A brand of highly durable and shock resistant watches owned by Casio.
GADA	‘Go anywhere, do anything’. A GADA watch is a durable timepiece that is capable of accompanying its owner to any environment from the office to the seas. A GADA watch is often the choice for a one-watch collection. Also see ‘one-watch collection’.
Galaxy	A nickname for certain examples of the Rolex Oyster Perpetual reference 6098 which feature hour markers in the shape of five-pointed stars. Also see 'Stelline', a ref.6062 Triple Calendar with the same indices.
Galvanized	In watchmaking, a galvanized surface is one that is covered in a paint that has been galvanically applied, i.e. using electrical processes akin to electroplating gold. The technique was used predominantly on dials meant to have gilt features. Also see 'gilt dial' and 'galvanized gilt dial'.
Galvanized Gilt Dial	A dial, usually copper or brass, whose plate is highly polished and/or covered in gold leaf which is exposed through layers of galvanically-applied paint through negative relief. The process can be done in two ways: the first being the etching of the paint to reveal the substrate and the second being the application of a transparent coating of the dial features before the paint is applied so that the paint does not stick. The latter process is more common and usually allows for more intricate and accurate patterns to be created via pad printing. The paint (which becomes the dial color) on top of the coated areas disappears when it is washed off or baked, revealing the dial plate's color. The baked product is then treated to a coating of glossy lacquer that seals in the dial and prevents oxidation of any exposed dial plate. Thus this dial style is often referred to as 'glossy gilt dial' or 'glossy galvanized dial'. The galvanized gilt dial is the most famous and iconic type of gilt dial, with many regarding o
Gasket	A deformable mechanical seal meant to provide sealing under compression between two married surfaces. In watchmaking it is interchangeable with the term 'o-ring', which is technically just one of the many types of gaskets. Gaskets are usually made of rubber or silicone and serve as important seals against water leakage and humidity. They can be found in virtually every orifice of a water resistant watch such as the crystal opening, caseback opening, and crown assembly.
Gay Frères	A defunct manufacturer of wristwatch bracelets established in Geneva, Switzerland in 1835. Gay Frères is indisputably one of the most important and prolific bracelet manufacturers in history, and is responsible for dozens of designs that still dominate the market today. Some Gay Frères creations include the Oyster, Jubilee, President bracelets for Rolex and the integrated bracelets for both the Audemars Piguet Royal Oak and Patek Philippe Nautilus. Gay Frères was acquired by Rolex in 1998 and ceases to exist as a separate entity in any way.
Gay Frères Bracelet	A bracelet made by the renowned bracelet manufacturer Gay Frères. Also see 'Gay Frères'.
Gear	A gear is a toothed wheel that rotates to transfer energy in a movement. In watchmaking, smaller gears are called pinions and larger gears are called wheels.
Gear Tooth Profile	The shape of a gear tooth, specifically the outline from the tip of the tooth to the root on one side of the tooth cross section. Technically each tooth has two profiles, which are usually symmetrical but sometimes asymmetrical. The profile determines various mechanical properties of the gear. In industry at large, the two major profiles are involute and cycloid profiles, with involute being the more modern and widely-used profile. Cycloid profile teeth are vestigially retained in watchmaking. Watchmaking also employs a great variety of profiles for functional and decorative purposes.
Geneva Drive	A mechanism that translates constant rotational movement into intermittent rotational movement. The mechanism is composed of two wheels: the driving wheel which constantly rotates and the driven wheel which intermittently rotates. The drive wheel is composed of a wheel with a single pin at its periphery and a small gibbous moon-shaped secondary disk on top of it. The disk meshes with the shape of the driven wheel to keep it in place when not in motion while the pin rotates until it meshes with a slot in the driven wheel. The pin enters the slot of the driven wheel and advances it as the driving wheel rotates. Because the driven wheel only moves when the lone pin makes contact, constant rotational movement is successfully transformed to intermittent movement. The mechanism is also called the ‘Maltese cross mechanism’ as the driven wheel often resembles a Maltese cross. In watchmaking, the Geneve drive is mostly used as a stopwork. See ‘Geneva stopwork’.
Geneva Stopwork	A stopwork that utilizes the mechanical principles of the Geneva drive. A driving wheel is mounted coaxially with the barrel to the mainspring arbor so that it rotates as the mainspring winds and unwinds. This driving wheel has a single protrusion (finger) which comes around every rotation of the barrel and meshes with a slot on the driven wheel. The driven wheel typically has only five slots and five arms. One of the arms is significantly bigger than the others and prevents the finger from rotating free of its slot once it meshes. This prevents the barrel from being overwound as it limits the number of rotations a barrel can perform. A side-effect of this is that it also prevents the barrel from completely unwinding, as the stopwork works both ways. While this does keep the barrel within its optimal torque region, it may inconvenience the wearer by having the watch stop prematurely if its power reserve is not replenished. Also see ‘Maltese cross mechanism’.
Geneva Stripes	See 'striping'. The city of Geneva is most closely associated with the technique, so any striping may be called Geneva striping regardless of where the watch is from.
Genuine Leather	A type of leather. Genuine leather is constructed of leftover leather scraps. It gets its name from how it is the minimum grade of leather that can still be considered leather.
George Daniels	(1926-2011) A watchmaker from London, England and based in the Isle of Man.
German Silver	An alloy used in the manufacture of watches. Also called 'nickel silver', 'maillechort', or 'Argentan'. German silver is predominantly copper mixed with a white metal such as nickel and/or zinc. It does not contain any silver. German silver was first manufactured by 18th century German metallurgists who were trying to imitate paktong, an alloy smelted directly from the ore. In watchmaking, German silver is most famous for being machined into bridges and plates of movements.
GF	In watchmaking, 'GF' could be an acronym for independent watchmaker Greubel Forsey or bracelet manufacturer Gay Frères.
Ghost(ed) Bezel	A bezel that has faded due to wear and time. Especially describes black bezels that have faded to a light gray.
Gilt Dial	A general term for a dial with contrasting metallic features, especially gold or gold-colored features against a black dial. In the most precise sense, a gilt dial is one of a brass or gold leaf substrate that is exposed through additional layers of galvanically-applied paint - usually black - until the entire dial is finished with lacquer coating to prevent oxidation of the exposed substrate. The desired parts of the substrate are left uncovered by paint through selectively applied transparent coating which prevents the paint from binding with the substrate. They may also be revealed by etching the paint off. To separate this somewhat antiquated but appreciated process from other techniques that produce similar aesthetics, these dials are called 'galvanized gilt dials'. In modern times it is more common to apply gold-colored paint.
Girard Perregaux	A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1791. Abbreviated ‘GP’. Girard Perregaux is owned by the Kering Group.
Giugiaro	A nickname for the Seiko reference 7A28-7000 and its reissue, reference SCED035. The watch was one of several Seikos designed by Italian design icon Giorgetto Giugiaro and certainly the most famous in part due to its appearance on the protagonist's wrist in the 1986 film Aliens. Also see 'Ripley'.
Gladius Hands	Another name for ‘sword hands’. This name was used mostly by Enicar.
Glaive Hands	See ‘sword hands’.
Glashütte Original	A watch manufacturer established in Glashütte, Germany in 1994 with claimed roots to 1845. Abbreviated ‘GO’ and alternatively written ‘Glashuette Original’ to render the umlaut in the English alphabet. Glashütte Original is owned by the Swatch Group.
Glashütte Stripes	See 'striping'. Used to describe striping done on German watches, especially those made in the Saxon town of Glashütte.
Glidelock	A quick adjustment extension system mounted onto certain Rolex Oyster bracelets. Glidelock allows the anchor of the bracelet to ‘glide’ across the length of the clasp when pushed. This allows for adjustment up to 20mm in 2mm increments. Glidelocks fitted to heavy duty divers like the Deep-Sea have an additional feature which allows for adjustment while on the wrist. While Glidelock makes the clasp larger than those with the more conventional Easylink system, it is a useful feature for dive watches.
GMT	Greenwich Mean Time. Refers a mean solar timezone based on the time at the Royal Observatory in Greenwich, England and includes all of the United Kingdom, Ireland, Morocco, Liberia, Mali, Mauritania, Senegal, Ghana, Togo, and others. GMT is the predecessor of UTC in its role as an international time reference, with time zones and local times still being referred to as positive or negative offsets of it. In colloquial English, GMT and UTC are used interchangeably even though they are different concepts - for most casual purposes this is accurate. However GMT is not deemed suitably accurate for navigational, astronomical, or geodetic purposes. Due to its similarity with UTC, GMT is also related to UT1. See 'UTC' and 'UT1'.
GMT Complication	A complication that displays another timezone with a 24-hour hand, called the 'GMT hand'. On rare occasions the movement may have a 12-hour GMT hand accompanied by a day/night or am/pm indicator instead of the much more common 24-hour hand. The GMT complication requires some sort of independently adjustable hour hand, be it the GMT hand itself, the regular hour hand, or both. Depending on which one is adjustable a GMT complication or a watch with such a complication may either be called a 'caller GMT' or a 'traveler GMT'. In addition to the extra hand, GMT complications almost always feature a date window and frequently feature a GMT/dual time bezel. The GMT complication is identical to the 'UTC complication' and has some mild overlap with the 'dual time complication'.
GMT Hand	A hand that displays the time of another time zone in a GMT complication. The vast majority of GMT hands are 24-hour hands, but some exceptions with a 12-hour rotation cycle do exist. The latter must be complemented by a day/night or am/pm indicator which informs the wearer which half of the day the GMT hand is on. Most GMT hands are centrally mounted on the center stack but some have their own subdials.
Gnomon	The part of a sundial that casts a shadow.
God Tier Casio	A watch collecting social media meme originating from Dutch watch dealer Nico Leonard’s YouTube videos where he consistently exalts the superior attributes and affordable price of Casio watches.
Going Train	A mechanism that transfers energy from the power source of the watch - the mainspring - to the parts that need to move such as the hands. It is a wheel train that primarily consists of the first, second, third, and fourth wheels.
Gold (Au)	An element often used in the manufacture of watches. Abbreviated Au. Gold is one of the most important metals in watchmaking and is used for crafting virtually any part of the watch including the case, indices, bracelet, hands, and movement. In watchmaking gold is rarely used on its own and rather incorporated into an alloy. Common alloys include yellow gold, red gold, pink gold, white gold, and rose gold. The purity of gold is measured in karats.
Gold-capped	A metal is gold-capped when a base layer is capped or fitted with a gold shell. Cap gold is at least 200 microns thick and is generally the thickest gold layer available short of solid gold. While cap gold can look exactly like gold from the dial-side, they almost always have stainless steel casebacks.
Gold-filled	A metal is gold-filled when a base layer is mechanically bonded with an outer layer of gold. Gold-filled watches contain far more gold than gold-plated watches, with gold occupying at least 5% of the metal's total weight. The gold layer is usually about 100 microns (0.1mm) thick.
Gold-plated	A metal is gold-plated when a base layer is chemically or electrically plated with a thin outer layer of gold. The gold layer is between 0.5 to 20 microns thick and will come off and expose the base metal with time. However, gold-plating is a relatively simple and affordable process that can be redone easily.
Goldberger’s Cheese Knife	A famous charcuterie knife (erroneously known as a cheese knife) which renowned collector John Goldberger used to open the casebacks of a Rolex reference 4113 split-seconds chronograph and an Italian Air Force Universal Genève reference 22560 to reveal their Valjoux 55 VBR movements. This event was witnessed by a great portion of the watch community as it was during an episode of Talking Watches, a popular series by New York-based watch media company Hodinkee. The nonchalant finesse with which Goldberger grabbed the nearby knife, scraped it clean on the sleeve of his tweed jacket, and pried open two priceless timepieces has become something of a legend in the watch community.
Golf Timezone	Military timezone name for UTC-7.
Gong	See 'gong spring'.
Gong Heel	A rectangular block of metal that holds the gong spring and fastens it to the case. Also called a gong foot.
Gong Spring	Also simply called the 'gong'. A thin strip spring that makes a noise when struck with a striker in a striking complication. The spring is typically mounted to the periphery of the movement. A movement may have more than one gong spring depending on the number of pitches it must make. If there are two gong springs they are typically tuned to bass and treble, with the lower sounds representing a larger unit of time (e.g. hours) and the higher sounds representing a smaller unit (e.g. minutes).
Governor	In a striking watch, the governor manages the tempo of the strikes. This is done by regulating the unwinding speed of the repeater mainspring.
Grail	See 'grail watch'.
Grail Watch	A watch that one would purchase if money were no object. The name is a reference to the Holy Grail, a legendary treasure from Arthurian legend.
Grain	The composition, texture, and appearance of an animal hide. Grain may also refer to the grain layer of an animal hide, which refers to the papillary portion. As such, cuts from the reticular layer are not referred to as naturally having grain.
Grains-of-rice Bracelet	See 'beads-of-rice bracelet'.
Grand Feu	(French) 'Great fire'. An alternative term for vitreous enamel. In most use cases, grand feu denotes a dial completely covered in a vitreous enamel coating and embellished with no other enameling technique like cloisonné, champlevé, and flinqué.
Grand Seiko	A watch manufacturer established in Nagano, Japan in 1960 and now headquartered in Tokyo, Japan. Abbreviated ‘GS’. Grand Seiko is owned by the Seiko Group.
Grande Sonnerie	(French) 'Big strike'. A strike sequence that chimes the hour and quarters since the hour every quarter in passing. In other words a grand sonnerie announces the current hour every time it announces the quarters, while the petite sonnerie foregoes the hour strike for every quarter except for each full hour. In modern times many watches are capable of switching between grand and petite sonneries.
Grande Taille	(French) Large size. Typically refers to a larger size offering of a certain watch. This nomenclature is most commonly associated with the Jaeger-LeCoultre Reverso.
Grandfather clock	See ‘longcase clock’.
Graver	A tool used for engraving.
Great Wheel	See ‘first wheel’.
Great White	A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 1665 with only white dial text as opposed to a combination of red and white.
Grenade Dial	A dial with grooves running horizontally and vertically, sometimes in a globular fashion. The name derives from its resemblance to the grooves and knobs on the surface of a fragmentation grenade. A grenade dial is similar to an embossed grid dial also known as a tapisserie dial, but the knobs on a grenade are significantly bigger and often rounded at the edges. In some watches like the Patek Philippe Aquanaut, the grooves are globular and closely resemble the shape of the iconic Mk 2 fragmentation grenade. Also see 'embossed checkered dial' and 'tapisserie dial'.
Greubel Forsey	A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 2004. Abbreviated ‘GF’. Greubel Forsey is privately owned.
Grönefeld	A watch manufacturer established in Oldenzaal, Netherlands in 2008. Grönefeld is privately owned.
GTG	Get-together. See 'meetup'.
Guard Dart/Pin	A sharp dart attached to the swallowtail of the pallet fork. The guard dart is designed to engage with the edges of the passing hollow of a roller in the event of a hard knock or shock that could throw the escapement off proper alignment and cause overbanking. Under normal operation, the guard dart does not touch any other component and merely passes through the passing hollow.
Guilloché	(French) A decorative technique where repetitive geometric patterns are engraved onto a surface using a rose engine via engine turning.
GV	Glace, Verte. Rolex nomenclature for a green sapphire crystal.
H-link bracelet	A two-link bracelet with a stack of H-shaped links interspersed by small rectangular links.
H. Moser & Cie.	A watch manufacturer established in Saint Petersburg, Russia in 1828 and now headquartered in Schaffhausen, Switzerland. H. Moser & Cie. is privately owned.
Habring^2	A watch manufacturer established in Völkermarkt, Austria in 2004. Habring^2 is privately owned.
Hack Watch	An antiquated term for a watch with hacking seconds. Specifically it refers to pocket watches carried around on a maritime vessel as portable timepiece synced to the not-so-portable marine chronometer. In the post-WWII era the term referred to several military-issued wristwatches with a hacking mechanism. Today, the universal proliferation of the hacking mechanism has antiquated the term.
Hacking	The act of stopping the seconds hand with the pull of the crown. A hacking function allows the wearer to stop the seconds hand when it is exactly at 0 seconds (twelve o'clock) where it can be more accurately set to a more accurate timepiece. While ubiquitous today, hacking was an important feature that was added to timepieces that needed to be extra accurate. It was relatively common in timepieces delivered to the armed forces, maritime vessels, and railways. Also see 'stop/hacking seconds' and 'hack watch'.
Hairspring	Also known as a balance spring. A spiral or helical torsion spring that allows the balance wheel to oscillate at a consistent frequency. The hairspring starts at the collet and terminates at the stud. The hairspring is as thin as a hair, hence the name. Not to be confused with 'mainspring'.
Half Hunter Case	A case with a hinged dial cover that has a transparent window in the middle. This allows the wearer to read the time without opening the cover. The name comes from the half hunter style of pocket watch which featured these covers. Somewhat common in pocket watches, they are rare in wristwatches but not unheard of. Also see 'hunter case'.
Half Hunter Caseback	A hinged caseback that has an exhibition window in the middle of the cover. The name comes from the half hunter style of pocket watches that had a hinged front cover with an exhibition window that allowed the wearer to read the time without opening it. While half hunter cases on wristwatches is rare but certainly extant, half hunter casebacks are virtually unheard of even though they are technically possible. Also see 'hinged caseback', 'hunter caseback', 'hunter case', and 'half hunter case'
Half-quarter Repeater	A striking complication that repeats (chimes) the hours and every half quarter (seven and a half minutes) that has elapsed since the last hour. Typically the hours are sounded with a bass note and the half-quarters with a treble note or one of each.
Hallmark	An official mark struck on a metal surface to certify an attribute of the object. While a hallmark may be any kind of such mark, in the narrowest sense it refers to a mark that attests the purity of a precious metal. Hallmarks differ according to period, country or region of manufacture, and other factors and can thus serve as valuable signifiers of the authenticity of a watch.
Hamilton	A watch manufacturer established in Lancaster, USA in 1892 and now headquartered in Biel/Bienne, Switzerland. Hamilton is owned by the Swatch Group.
Hammer	A percussion device that strikes a gong-spring in a striking watch. A hammer is usually shaped like an axe.
Hammer (chronograph)	A component of a chronograph mechanism which strikes the reset cam in order to reset the chronograph back to zero. The hammer is usually an axe or club-shaped heel at the end of the reset lever.
Hammer Spring (chronograph)	A component of a chronograph mechanism which applies constant pressure to the reset lever.
Hammer Trip	A beak mounted onto a pivot which activates the hammer. As the direct input for the hammer, the trip interacts with the teeth on the bottom of a rack and actuates the hammer once for every tooth that passes through it.
Hammy	A nickname for Hamilton watches.
Hand-wound Movement	A movement which must be wound manually. Synonymous with 'manually-wound' and 'manual wind'. For the vast majority of cases, refers to a type of mechanical movement although there are some exceptions like manually-wound hybrid movements. Also called simply a 'mechanical movement' by some although this term can be technically erroneous and potentially confusing.
Hands	The moving components of a clock that displays information by pointing.
Handset	The complete set of hands on a single clock regardless of function. Usually of a consistent style.
Handstack	The stack of hands that are mounted on top of each other.
Hanhart	A watch manufacturer established in Diessenhofen, Switzerland in 1882. Despite still being headquartered in Diessenhofen the company manufactures in Schwenningen, Germany. Hanhart is privately owned.
Hard Case	A form of watch storage designed for maximum protection of the stored goods from impact, abrasion, water, dust, and humidity. The external shell is usually hard plastic and/or rubber and the interior is typically lined with thick and soft foam padding. Unlike most watch cases and boxes which are designed stylishly, hard cases are utilitarian. They typically come with aggressive ribs and buttresses to absorb impact and have large carry handles. Many come with internal locks or holes for padlocks.
Haute Horlogerie	(French) High horology. A term that describes watchmaking as an art form as opposed to more practical or pedestrian watchmaking. While there is no clear definition or boundary, the term usually refers to timepieces crafted with exquisite materials, lavish embellishments, and/or complicated mechanics by master craftsmen. Generally, a watch that is simply expensive or rare is not considered haute horlogerie if it does not possess the aforementioned characteristics.
Haute Horology	A macaronic Franglais term that is in between the French term 'haute horlogerie' and its corresponding English term 'high horology'.
Heart Piece Cam	In a chronograph, ‘heart piece cam’ can either refer to the reset cam which resembles a human heart or the cam that serves as the control system in a cam chronograph. The former use is far more common.
Height	The perpendicular length of the watch from a flat surface. It is also commonly called the 'thickness'. Height mostly refers to the case height, which measures from the caseback to the bezel, excluding any protruding crystal. If the height of the crystal is included in the measurement it is usually mentioned.
Helium Escape/Release Valve (He-valve/HEV)	A one-way valve that allows pressurized helium atoms to escape the case of a dive watch so that the accumulated pressure inside the watch does not blow out the crystal when the diver resurfaces. Dive watches are generally impervious to water but cannot stop helium as it is the smallest atom on the periodic table. Helium is heavily used by saturation divers in their mixed breathing gases which help them reduce the risk of nitrogen narcosis in deep dives or long stays underwater. An HEV redirects the helium out of the watch while still keeping larger particles such as water molecules out so that there is no accumulation of pressurized helium in the watch that may cause an explosion when there is no longer equivalent water pressure pushing down on the crystal. While not really an essential feature on deep divers, HEVs have become loved by marketing departments.
Hell Diver	A nickname for dive watches with a water resistance of 666ft (202m). The name comes from the ‘number of the beast’ or the ‘devil’s number’. Several dive watches from the 1960s and 1970s had this water resistance including those made by Bulova and Caravelle. 666m is much less common, but it would still qualify as a hell diver.
Helmet	A nickname for the Seiko 6139-710X series automatic chronographs that have bulky cases that somewhat resemble the so-called coal scuttle profile of the WWII-era German Stahlhelm. The black variant of the Helmet chronograph is also called the 'Darth Vader'. In Japan, the Helmet is called the 'Fujitsubo', a name it shares with the so-called 'Tokei Zara'.
Hesalite	Omega's brand of acrylic watch crystal.
Heures Sautantes	(French) Jumping hours.
Hidden Clasp	Any clasp that is hidden from view. Usually a single or double-fold clasp, the hidden clasp is usually found on bracelets but also rarely on straps. Hidden clasps contribute to a sleek design and also may provide for a less bulky and more comfortable wearing experience. A hidden clasp's location may be subtly hinted by the existence of push buttons at the sides, a latch or button on the bracelet, or nothing at all.
Hidden Lugs	A style of lugs that are completely obscured from the top view. This style usually comes in the form of a cutout for the strap ends on caseback-side. Hidden lugs can also include some varieties of shrouded/hooded lugs.
High Horology	A term that describes watchmaking as an art form as opposed to more practical or pedestrian watchmaking. A direct translation of the French term 'haute horlogerie' which is also commonly borrowed into English as is or as the Franglais term 'haute horology'. While there is no clear definition or boundary, the term usually refers to timepieces crafted with exquisite materials, lavish embellishments, and/or complicated mechanics by master craftsmen. Generally, a watch that is simply expensive or rare is not considered high horology if it does not possess the aforementioned characteristics.
Hinged Caseback	A caseback that has a hinged cover that allows it to be opened. A hinged caseback would have two components: the hinged cover and the caseback itself. Hinged casebacks originate from small pocket or pendant watches that were converted into wristwatches during the incipiency of the wristwatch. Hinged casebacks come as standard on most pocket watches but is considered a novelty feature on modern wristwatches. They often reveal a display caseback under the cover, which offers the benefits of both a solid and display caseback. Also see 'officer caseback', 'hinged dust cover', 'hunter caseback', and 'half hunter caseback'.
Hinged Dial/Front Cover	A dial-side cover mounted on a hinge that allows it to be opened. In pocket watches with open faces, i.e. with no transparent crystal, the hinged cover allowed the owner to read the time when needed and keep the case closed when the watch was stored away. Today, cases with these covers are known far better as hunter cases. Also see 'hunter case' and 'savonnette'.
Hinged Dust Cover	An alternative name for a hinged caseback. Used by Patek Philippe. The name originates from how the hinged cover on pocket watches would prevent dust and foreign materials from entering the holes for the winding key on older pocket watches. Before the adoption of crowns, pocket watches had to be would and set by inserting a key into a hole in the caseback. The hinged dust cover was a necessary solution to this. Also see 'hinged caseback', 'hunter caseback', 'officer caseback', and 'half hunter caseback'.
Hodinkee	An online watch publication based out of New York City, USA.
Hollow End Link	An end link that is constructed of hollow, usually stamped metal. Hollow end links may consist of two components which must be assembled to serve as a complete end link. Hollow end links are lighter than solid ones but can be rattly, tinny, and flimsy. They are commonly found on vintage watches and on more affordable modern bracelets. Also see 'solid end link'.
Holy Grail	See 'grail watch'. The term may also refer to a watch of an exceeding rare reference or condition.
Holy Grail (Omega)	A nickname for the Omega Speedmaster Automatic reference 376.0822. While the ref.376.0822 is by no means the rarest or most valuable Omega, the nickname comes from the personal journey of renowned collector Chuck Maddox to add the watch to his collection. Maddox’s well-documented and widely-read account of his hunt put his nickname for the watch into mass circulation and has since cemented itself as the standard epithet for the ref.376.0822.
Holy Grail (Seiko)	While the name 'Holy Grail' can describe many watches in the vast catalogues of Seiko, it typically refers to the Seiko 5 Sports reference 6138-8010 Speed-timer automatic chronograph. The name comes from the watch's highly-coveted design and rarity.
Holy Trinity	In watchmaking, the Holy Trinity refers to an unofficial triad of prestigious watch manufacturers deemed to be at the pinnacle of watchmaking, namely Patek Philippe of Geneva, Vacheron Constantin of Geneva, and Audemars Piguet of Le Brassus. In reality most horologists and enthusiasts do not take this term seriously.
Homage	A clock, usually a watch, which heavily references if not outright copies the design of another but uses a different brand name. Technically homages are not counterfeits or replicas but have about as much originality.
Home Plate	A nickname for the Tudor Oysterdate reference 7031. The name comes from the shield-shaped hour markers which resemble baseball home plates.
Home Time	The time where one's home is, or one's reference timezone.
Hooded Lugs	A style of lugs where the space between the lugs is obscured with some sort of metal cover, either fixed or articulating. Also known as ‘shrouded lugs’. Hooded lugs can overlap with hidden lugs, especially the variants where the lugs, not only the space between, are also covered by an extension of the case.
Hooke’s Law	As the extension, so the force (Latin: ut tensio, sic vis). An empirical law which states that the force needed to extend or compress a spring by a certain distance is linearly proportional to the distance. In watchmaking where the important springs in question are spiral spring, this law can be applied to state that the torque exerted by the mainspring is linearly proportional to its angle of rotation. This is important because mainsprings do not always follow Hooke’s law. When the mainspring is fully wound, it cannot absorb any more energy so excess turning force from winding the stem goes elsewhere. When the mainspring is nearly fully unwound, the spring pushes outward agains the inner barrel wall and exerts disproportionately low torque. Keeping the mainspring operating within its optimal range where it follows Hooke’s law is key to enhancing the accuracy of a timepiece as the torque output determines the speed of the movement.
Horloge	(French) A watch or clock.
Horn Lugs	A style of lugs that resemble animal horns. They are bulbous at the base and come to a sharp tip, usually with a curve. The most famous of these would likely be the ‘cornes de vache’ or cow horn lugs. See ‘cornes de vache’.
Horologist	A person who studies horology. Also a fancy term for a watch enthusiast. In the past, horologists studied time itself, timekeeping, and manufactured timekeeping devices. Today the three disciplines are usually separate.
Horology	The study of timekeeping devices. While the term literally means 'the study of time', horology focuses more on the human measurement of time rather than the properties of time itself. In the modern context, horology refers broadly to the study of timekeeping instruments. The similar term 'chronometry' refers to the science of timekeeping and its standards. The watch collecting hobby is more appropriately placed within the realms of horology as it concerns timekeeping devices more than time itself. However, there is significant overlap and neither horology nor chronometry is complete without the other.
Hotel Timezone	Military timezone name for UTC-8.
Hour Hand	The hand that points to the hour. Usually makes a full rotation every twelve hours, with the exception of a few watches with 24 hour displays.
Hour Rack	A rack which interacts with the hour snail and the hammer trip of the bass hammer. It is lined with twelve teeth, one for each hour of the dial.
Hour Recording Wheel	A component of a chronograph which moves the chronograph hour hand.
Hour Snail	A snail cam which transmits information on the current hours to the hour feeler so that a repeater can announce the current hours. The hour snail is in the shape of a logarithmic spiral with four steps.
Hour Wheel	A component of the motion work that rotates the hour hand. The hour wheel consists of a wheel and a pipe, the latter of which mounts the hour hand. The wheel meshes with the minute wheel pinion and turns once every twelve hours. The hour wheel sits on the top of the shaft of the cannon pinion and is the directly under the dial. It is separated from the dial via a dial washer.
Hublot	A watch manufacturer established in Geneva, Switzerland in 1980 and now headquartered in Nyon, Switzerland. Hublot is owned by LVMH Moët Hennessy Louis Vuitton.
Hulk	A nickname for the Rolex Oyster Perpetual Submariner reference 116610LV, a Submariner with a green dial and green ceramic bezel insert. The name is a reference to the green color of the dial and bezel.
Hunter Case	An alternative name for a hinged dial cover. A case with a cover on the dial-side. This protects an open-face watch from breakage, which is no longer a concern today with sapphire crystals. Today the cover serves an aesthetic or stylistic purpose. The name comes from the hunter style of pocket watch which commonly featured these covers. Very common in pocket watches, they are very rare in wristwatches but not unheard of. See 'hunter watch', 'savonnette', 'half hunter case', and 'hinged dial cover'.
Hunter Caseback	An alternative name for a hinged caseback. The name 'hunter' comes from the hunter style of pocket watches, which featured a spring-loaded hinged cover. Technically, the term 'hunter caseback' is not fully accurate as the hunter watches featured their iconic covers on the dial-side, with the movement-side having the usual hinged caseback. See 'hinged caseback', 'half hunter caseback', 'hinged dust cover', and 'hunter case'.
Hunter Watch	A pocket watch that features a hinged front cover and savonnette movement. These watches were marketed as hunter watches in America, which prompted manufacturers to engrave elaborate hunting scenes on the case. Also see 'savonnette'.
Hybrid Movement	One of the three major types of movements. A movement which combines some components of mechanical movements and some components of electronic movements. Examples include electric movements which use an electric battery to power a mechanical balance or a tuning fork, or Seiko's Spring Drive movements which use a mechanical gear train to power an electronic integrated circuit which keeps time and an electromagnetic brake which regulates the movement.
Hydrogen (H)	An element that is sometimes used as the frequency reference in atomic clocks. They are more specifically known as hydrogen maser clocks.
HYT	A watch manufacturer established in Neuchâtel, Switzerland in 2012. HYT is owned by Kairos Technology Switzerland.
Hz	A unit of frequency that measures actions per second. One noteworthy point is in a mechanical movement, an oscillation is regarded as a single action. Therefore, two semi-oscillations or two beats constitute a single action. This means that when converting bps or vps to Hz, the value is halved. For example, a watch that ticks ten times per second runs at 10 bps or 10 vps. However, in Hertz, it runs at 4 Hz. Meanwhile, this is not the case for a quartz movement. A quartz movement that vibrates at 32,768 vps is in fact vibrating at 32,768 Hz.
Ice	A colloquial term for diamonds.
Ice-blue Dial	A dial with a metallic light blue color. In Rolex watches, the ice-blue dial means that the watch is made of platinum.
Iced Out	A colloquial term for a watch that has been set with diamonds.
Impermeable	(French) Waterproof. See 'waterproof'.
Impulse Face	The surfaces of an escape wheel tooth and pallet jewel which come into contact with each other during the impulse of the escapement.
Impulse Jewel	A component of the balance that strikes the pallet fork horns. The function of the impulse jewel is to relay impulses from the pallet fork to the balance which allows the balance to operate, and to strike the pallet fork at the frequency that the balance swings which allows the pallet fork to seize and release the escape wheel at the speed dictated by the balance. It is a small semi-cylindrical jewel (typically a ruby) that protrudes from the impulse roller. It is also known as a ‘roller jewel’, ‘impulse pin’, ‘impulse jewel’, and ‘cheville’.
Impulse Pin	See ‘impulse jewel’.
Impulse Roller	The main roller, particularly in the context of a double roller escapement where differentiation in terminology from the smaller safety roller is necessary.
In Passing	In a striking watch, a strike in passing is activated at certain predetermined times. Antonymous with 'on command'. Examples of strikes in passing are grande and petite sonneries, which chime only at designated times such as each full hour and quarter-hour.
In the Metal	In person. A play on the phrase 'in the flesh'.
In-house	Executed internally by the company. The term has no clear standard as to what it means. Thus it is used more liberally by some than others. In-house most commonly refers to the movement which is usually the most difficult and complicated aspect of watchmaking and therefore commonly outsourced. However the term can refer to absolutely anything. Antonymous with 'outsourced'.
In-house Movement	A movement both developed and produced internally by the watch manufacturer. As it is virtually impossible for any company to produce absolutely all the parts needed for a watch movement, the term does not have an exact standard. Most in-house movements are designed in-house and manufactured almost entirely in-house, while using some readymade components. Some self-described 'in-house' movements are based on ébauches but are so heavily modified that they are unrecognizable. What makes a true in-house movement is the subject of debate. See 'proprietary movement' for a similar term, 'ébauche' for an opposite term, and 'third party movement' for a related term.
In-line Display	A style of display where the assets are arranged in a single line. Typically used for mechanical perpetual calendars where the in-line arrangement requires a high degree of mechanical complexity.
Independent	An independent watch manufacturer that is not a part of a parent company. While independents come in many shapes and sizes, many independents revolve around a single master watchmaker or a small team of them with a concentrated vision and a focus on horological engineering. Therefore, companies like Patek Philippe which are not owned by anyone else but are still corporate in structure are not considered independents. Very small scale brands that focus more on factors other than movement engineering are called 'microbrands' and are referred to more commonly as such. Therefore, to describe a company as 'independent' is different from describing it as 'an independent'.
Independently Adjustable Hand	A hand - usually an hour hand - that can be adjusted without resetting the watch. Normally one must pull out the crown to its setting position to move any of the hands. Independently adjustable hands can be set at a dedicated crown position or with a pusher or corrector. This feature is commonly seen in watches that can display multiple timezones.
Index (dial)	A marking on a dial which indicates the hours. Synonymous with 'hour marker'. 'Indexes' and 'indices' are both acceptable plural forms of index. Indices can be numerals, but the term usually refers specifically the geometric shapes such as sticks, rectangles, circles, and others that are used in lieu of numbers.
Index (movement)	A lever that adjusts or serves as a visual reference for the regulator.
Index Hands	See ‘baton hands’.
India Timezone	Military timezone name for UTC-9.
Indie	A term denoting microbrands, some independent manufacturers, and other smaller watch manufacturers. While the term 'indie' normally means 'independent', the word is used to refer to a slightly larger group of watch brands than 'independent'. As with many of these conceptual terms, the terminology is not clear-cut.
Indirect Center Seconds	An arrangement of center seconds where the fourth wheel is not at the center of the movement and thus requires gearing that connects the fourth wheel to a wheel at the center which drives the seconds hand. Indirect center seconds maintains the conventional and traditional layout of a mechanical movement but makes the movement thicker due to the additional gearing and hinders precision, especially because of the addition of a tension spring to ensure the seconds hand moves normally despite being far and away from the power source that is the mainspring. Indirect center seconds can usually be identified with an extra bridge on top of the movement to hold the extra gearing, but is no longer common due to the proliferation of the mechanically superior direct center seconds.
Inertia Block	A disc-shaped weight that can be added or removed from the inner rim of a cam-poised/inertia/masselotte balance wheel to adjust the amplitude of the wheel. Also called by its French name 'masselotte'.
Integrated Bracelet	A bracelet that is built into the watch head and is not designed to be removable. Integrated bracelets are distinguished by an absence of lugs or the use of extremely proprietary lugs that would only fit the intended bracelet. Like most watch parts, even an integrated bracelet is technically removable and replaceable with a custom-made alternative or authentic parts. However the process would be exceedingly more difficult than with a conventional watch which uses spring bars, conventional lugs, and band. Also see 'integrated strap'.
Integrated Chronograph	A chronograph mechanism that is designed as a native part of a movement as opposed to a separate mechanism that can be attached to a movement. Antonymous with ‘modular chronograph’. Integrated chronographs can be more difficult to design as the inherent complexity of chronographs poses obstacles to the design process. However, they often have many technical advantages especially in thinness, architecture, and mechanics. Integrated chronographs often have a more dispersed architecture which makes for smoother operations and ease of servicing.
Integrated Circuit (IC)	A set of electronic circuits placed on a single chip surface made of semiconductor material like silicon. Also known as a chip, IC chip, microchip, and IC. An IC is an essential component on a quartz watch and some hybrid movements. It converts energy (usually from an electrical power source like a battery or capacitor) into pulses which activate the quartz oscillator, and then converts the vibration pulses of the quartz oscillator into a reduced signal for the motor - which moves the hands of an analog watch - or a LCD/LED display. In a way the IC 'counts' the vibrations of the quartz oscillator and makes sure that the seconds hand advances once for every pre-determined number of vibrations. Usually that number is 32,768 vibrations per second.
Integrated Lugs	Lugs that have no clear border with the case. A famous style is cushion lugs.
Integrated Strap	A strap that is built into the watch head and is not designed to be easily removable. Integrated straps are distinguished by an absence of lugs or the use of extremely proprietary lugs that would only fit the intended strap. Like most watch parts, even an integrated strap is technically removable and replaceable with a custom-made alternative or authentic parts. However the process would be exceedingly more difficult than with a conventional watch which uses spring bars, conventional lugs, and band. Integrated straps are almost always resin or rubber and are much rare than integrated bracelets. Also see 'integrated bracelet'.
Intermediate Wheel	A wheel whose sole purpose is to connect two moving components that are far apart and transfer input. Intermediate wheels are common in mechanical movements and can almost always be found in the keyless works. See ‘intermediate wheel (keyless works)’. Intermediate wheels also play a key role in chronographs. See ‘intermediate wheel (chronograph)’.
Intermediate Wheel (keyless works)	A component of the keyless works that meshes with the sliding pinion of the crown stem and the minute wheel in order to set the time. The intermediate wheel is normally disconnected from the crown stem because the sliding pinion is retracted unless the crown is pulled to the setting position. Keyless works typically have one or two intermediate wheels.
Intermittent/Intermediate Wheel (chronograph)	A component of a chronograph mechanism which receives input from the finger of the chronograph runner (chronograph seconds wheel) and transfers it to the minute recording wheel. As it is mounted on a bridge attached to a sliding lever, it is also known as a ‘sliding wheel’.
Involute Profile	A gear tooth profile based on an involute as opposed to a cycloid. An involute of a circle is a spiral that follows the path of a string unraveling from a point on a circle. In simple terms, an involute profile is round and bulbous , with no straight flank. This is in contrast with the relatively straight-sided cycloid profile. Originally an evolution of the cycloid, the involute profile is by far the most dominant profile in industrial gearing thanks to its constant pressure angle, superior longevity, smoothness, and ease of manufacturing. However, the opposite is true in watchmaking where cycloid profiles have clear advantages.
Isochronism	The property of a mechanical oscillator to maintain a constant oscillation period irrespective of oscillation amplitude, or the ability of a mechanical oscillator to maintain a fixed cycle despite variable amplitude. This means that a mechanical oscillator (e.g. a balance, pendulum, etc.) will take the same amount of time to complete an oscillation even if its angle of movement differs for every oscillation. For example, a balance wheel is isochronous if a 210, 215, and 220 degree swing all take 0.1 seconds to complete. Isochronism is central to accuracy as it is essentially a timekeeping organ’s ability to keep consistent time notwithstanding various mainspring power levels, temperatures, shocks, and vibrations which may impact the amplitude of the balance.
Issued Watch	A watch that has been issued by an organization of governmental and/or military nature. Militaries, intelligence organizations, and government foreign services often issued watches to their operatives for various reasons throughout history. These watches are often the subject of discussion, adoration, collection, and research in the watch community due to the stories involved, the relative rarity of these pieces, and the fact that issued watches are mostly a thing of the past. Some issued watches have special markings that indicate them as government property or certain modifications to meet military requirements.
IWC	A watch manufacturer established in Schaffhausen, Switzerland in 1868. The name stands for 'International Watch Company'. IWC is owned by Richemont.
J. B. Champion	A nickname for the Patek Philippe reference 2458 in platinum housing movement number 861121, an observatory-certified movement that was trialed in 1948 and one of only two Patek observatory movements ever cased in a wristwatch. The watch takes its nickname from the man it was delivered to, and bears his name on the dial. Joe Ben Champion (1917-1975) was a Texan lawyer who possessed several Patek Philippe creations.
Jaeger-LeCoultre	A watch manufacturer established in Le Brassus, Switzerland in 1833. Abbreviated ‘JLC’. Jaeger-LeCoultre is owned by Richemont.
James Bond	A nickname for the Omega Seamaster reference 2541.80.00 worn by Irish actor Pierce Brosnan as MI6 agent James Bond in the 1995 film GoldenEye.
James Bond (Rolex)	A nickname for the Rolex Oyster Perpetual Submariner reference 6538, which was worn by Sean Connery as MI6 agent James Bond in the 1962 film Dr. No. This reference is also known as the ‘Big Crown’ due to its oversized crown.
James Cameron	A nickname for the Rolex Oyster Perpetual Deepsea references 116660 and 126660 which accompanied film director James Cameron in his record-breaking descent to the bottom of the Mariana Trench in 2012.
Japanese Day Wheel	See 'Kanji date wheel'.
JDM	Japanese Domestic Market. It may also stand for 'Japanese Domestic Model' or 'Japanese Domestic Manufacture'. All three meanings are roughly the same, as the Japanese market almost always gets Japanese-made models from domestic manufacturers anyway. The term is used in the watch world just as it is in the automotive world. JDM watches are sought after by collectors for their purportedly superior quality, special editions, Japan-exclusive models, or relative rarity.
Jean-Antoine Lépine	(1720-1814) A horologist from Challex, France and active in Paris. Lépine was the King’s Clockmaker under Louis XV, Louis XVI, and Napoleon Bonaparte. He was a master of Abraham-Louis Breguet. Lépine is most noted for the Lépine caliber which radically thinned movements and made the archetypal pocket watch possible. He is possibly the first to employ bridges in clockwork architecture. Some other of his numerous contributions include keyless works, toothed mainspring barrel, deadbeat seconds, and improvements on repetition and moon phase. His tremendous innovations on watch aesthetics are often misattributed to his protégé.
Jean-Claude Killy	A nickname for the Rolex Oyster Chronograph reference 6236, and sometimes broadly the entire Rolex 'Dato-Compax' range including references 4768, 4767, 5036, and 6036. The name comes from French alpine ski racer Jean-Claude Killy who allegedly owned a ref.6236. While this is unfounded, the association will likely not disappear.
Jedi	A nickname for the Omega Seamaster reference 145.0024. The watch was one of the Star Wars triad nicknamed by renowned collector Chuck Maddox alongside the ref.145.023 ‘Anakin Skywalker’ and ref.145.0023 ‘Darth Vader’. The triad share their distinctive large shell and utilize the same cal.861 movement - essentially they are the same watch with small variations in dial composition and case shape. This distinction is important as the Jedi nickname is usually misattributed to the ref.176.0005, a completely different watch with little in common with the ref.145.XXXX series. This was due to a cataloguing error by watch auction house Antiquorum.
Jewel	In watchmaking, 'jewel' refers to a jewel which is used in a clock movement. Jewels are used as more durable, corrosion-resistant, temperature-stable, and lightweight alternatives to metal for surfaces or components where high levels of constant friction are expected. These jewels are usually synthetic but may occasionally be natural. Most jewels are based on corundum. Contrary to certain popular understandings, the jewel count of a movement does not determine how expensive or exquisite it is, though a higher jewel count may hint at a more complex movement. Jewels can be classified by into holed, cap, roller/impulse, and pallet jewels.
Jeweled Crown	A style of crown adorned with a jewel. The jewel serves a purely aesthetic purpose.
Jo Siffert	A nickname for the Heuer Autavia reference 1163T chronograph. The name comes from Formula One racing driver Jo Siffert, who famously wore the watch. The sponsorship deal between Siffert and Heuer was the first watch sponsorship in F1 history.
Jochen Rindt	A nickname for the Heuer Autavia reference 2446 chronograph. The name comes from Formula One racing driver Jochen Rindt who famously wore the watch. Also see ‘Nina Rindt’ for the Universal Genève chronograph worn by and named after his wife.
John Arnold	(1736-1799) A horologist from Cornwall, England and active in London. Arnold is credited with catalyzing the rapid development of portable timepiece accuracy, popularizing and possibly inventing the word ‘chronometer’, greatly improving the bimetallic compensation balance, inventing the pivoted detent and spring detent escapements, overcoil balance spring, and likely the concept of the tourbillon.
John Harrison	(1693-1776) A horologist from the West Riding of Yorkshire, England and active in London. Harrison is credited with the invention of the marine chronometer which was a crucial device in the projection of British military and commercial power across the seas. He also invented the gridiron pendulum and the grasshopper escapement among several other modifications to existing technologies.
John Player Special	A nickname for a variant of the Rolex Cosmograph Daytona references 6239, 6241, and 6264 'Paul Newman' in yellow gold with a black dial and gold sub-registers. The name 'John Player Special' is a reference to the tobacco company, whose black-and-gold livery adorned the Lotus 76, 77, 78, and 79 Formula One cars.
JPS	See 'John Player Special'.
Jubilee Bracelet	A five-link bracelet with narrow and short semicylindrical links and single-fold clasp produced by Rolex. The original bracelets were made for Rolex by Gay Frères. The Jubilee bracelet comes with a wide range of models including the Datejust, GMT-Master II, and Sky-Dweller. Due to its iconic status the bracelet has been widely mimicked and copied.
Juliet Timezone	Military timezone name for local time. Any timezone where the observer is currently located can be denoted ‘Juliet time’ or ‘J’, e.g. 0630J.
Jumbo	The larger variant of a watch. The term may also refer to an 'oversize(d) watch'.
Jumbo (Omega)	A nickname for the Omega reference 2505 and other similar 38mm watches made by the company in the 1940s and 1950s. The name comes from the watch’s large size compared to its contemporaries, as the average men’s wristwatch was usually no larger than 35mm at the time.
Jumbo (Seiko)	A nickname for the Seiko 6138-300X series chronographs which have large dials and cases.
Jump	The act of moving instantaneously as opposed to continuously.
Jumper	A type of component that consists of a flat spring that applies force to another component to keep it in place, restrict its movement until deliberately actuated, or control the speed of movement. Jumpers can be frequently seen applying force to wheels, levers, and yokes and are used commonly in mechanical movements.
Jumping Hours	A mechanism and display style of the hours where the hours are digitally represented and ‘jump’, or instantaneously change. Due to the ambiguity of the term ‘jump’, the term may also refer to an analog hour hand that is designed to jump ahead once every hour as opposed to continuously moving. The latter use is incredibly rare.
Kakume	(Japanese) A nickname for the Seiko 6138-003X series automatic chronographs. The name means 'square eyes' in Japanese, a reference to the square sub-registers.
Kamikaze Watch	A nickname for the Tensoku watches worn by Japanese pilots during the Second World War. There is no direct relation between Tensoku watches and kamikaze attacks, even though it is not unlikely that at least a few were on the wrists of Mitsubishi A6M pilots in suicide attacks. Also see 'Tensoku'.
Kanji Day Wheel	A day wheel with the days of the week written in the Sino-Japanese script Kanji. Synonymous with 'Japanese day wheel'. Kanji wheels typically feature only one distinguishing character but longer apertures may allow for the display of all three characters. They are common in Japanese watches made for the domestic market but are seen as collectible overseas.
Keeper	A loop that retains a strap. Keepers are used to keep extra strap length tidy and flush to the wrist. Keepers may be fixed or floating, with most straps having one fixed and one floating keeper.
Kermit	A nickname for the Rolex Oyster Perpetual Submariner reference 16610LV, a special edition of the Submariner celebrating the 50th anniversary of its introduction. The name is a reference to the lime-green color of the stainless steel bezel insert.
Keyless Works	A group of mechanisms including the crown and the components it controls. In other words, a group of mechanisms that deals with the setting and/or winding of a clock. Like most curious terms, ‘keyless works’ is a relic of the distant past. Clocks used to be wound and set by a pair of small keys which were inserted into holes in the case that gave access to the movement. The ‘keyless’ works eliminated the need for this by adding a component called the ‘crown’ which could be used to set and wind the clock. Thus, the crown and its associated components which form the winding and setting mechanisms became known as the keyless works.
Khanjar	(Arabic) A J-shaped dagger of Omani origin. In watch collecting nomenclature, a ‘Khanjar’ is the national emblem of Oman or a variation of it that was printed onto the dial, engraved on the caseback, or marked on the documentation and packaging of a watch gifted by Sultan Qaboos bin Said Al Said (r. 1970-2020) of the Sultanate of Oman. The Khanjar came in three different colors, perhaps reflecting the three national colors of the country: white, red, and green. It also came in three styles: the national emblem, a crowned national emblem, and the crest of the Royal Oman Police. Also see ‘Oman dial’ and ‘Qaboos dial’.
Kids' Watch	A watch designed for children. Typically the watch is designed to teach children how to read analog clocks and familiarize them with time.
Kilo Timezone	Military timezone name for UTC-10.
Kim Il Sung Watch	A watch ordered by the North Korean government during the reign of Kim Il Sung (r. 1948-1994) and bearing his signature. Orders for these watches peaked in the 1970s for the event of Kim's 60th birthday in 1972. The most famous and desirable examples were manufactured by Omega, with Kim's signature taking precedence over the Omega signature. The watches often came with Korean day wheels.
Kirazuri	(Japanese) A nickname for Grand Seiko watches with 'kirazuri' dials, including the reference SBGA387. Kirazuri is a finishing technique in Japanese woodblock printing that uses mica powder to add sparkle. The kirazuri dials mimic this effect, but with a textured metal plating over the dial plate instead of mica. The resulting texture is similar to that of a linen dial, but with noticeably more sparkle and variation in density.
Kite Hands	See ‘diamond hands’.
Knight	A nickname for the Seiko references SKXA47/49/51, SHC053/55, and SMY089 divers. The SKXA series is automatic, SHC quartz, and SMY Kinetic. The etymology of the nickname is unclear.
Knocking	See ‘overbanking’.
Komfit Bracelet	A thin mesh bracelet with a sliding clasp and adjustable straight end. The Komfit bracelet is renowned for its high adjustability thanks to its sliding clasp and compressible straight end link which can accommodate multiple lug widths. Thanks to this adjustability, the bracelet became a popular choice for astronauts in NASA and became an iconic pair with the issued Speedmasters of the era.
Korean Day Wheel	A day wheel with the days of the week written in Korean. Quite rare, Korean day wheels were most famously used in watches ordered by the North Korean government.
L Stone	A rare term for the exit pallet of the pallet fork. Presumably short for ‘left stone’ as the exit pallet is on the left arm of the pallet fork from the balance’s point of view. Also called the ‘discharging stone’.
L Swiss Made L	A marking that indicates that the dial contains photoluminescent paint such as strontium aluminate. This marking is optional as photoluminescent paint is not radioactive and virtually harmless to the human body even after direct exposure.
Lacquer	A resin or wax coating on top of a wooden or metal surface. In watchmaking, lacquer is most commonly found as a dial finish.
Ladder Bracelet	A bracelet with short center links and large spaces between them. Sometimes bamboo bracelets are called ladder bracelets, but ladder bracelets usually refer to oyster-style three-link bracelets whose empty spaces' sole purpose is ventilation or style.
Ladies' Watch	See 'women's watch'.
Lance Hands	See ‘alpha hands’. In common parlance, lance hands are generally a bit thinner than alpha hands.
Landshark	A nickname for the Seiko 5 Sports SKZ2XX series expedition watches. The nickname likely comes from the fact that the watch looks like a dive watch but is intended for use on land. It is also known as the 'Atlas'.
Lantern Clock	A clock style with a box body and a hemispherical bell suspended on the top, resembling a lantern. Lantern clocks were often mounted to walls but there were also variations which utilized pedestals. Later evolutions of the lantern clock which did not use weight-driven movements (which required clearance for the suspended weight and rope/chain) were mounted on footed bases. Lantern clocks also influenced the development of wadokei, or Japanese clocks.
Lateral/horizontal Clutch	A chronograph clutch system that is arranged horizontally. A horizontal clutch is the more conventional and traditional arrangement where the driving wheel, coupling wheel, and chronograph runner (chronograph seconds wheel) are connected horizontally via meshing leaves. Lateral clutches may suffer long term wear due on the teeth. They are also prone to wobbly seconds hand movement upon starting and cause a drop in amplitude which may negatively affect the accuracy of the watch. While technical traits are in favor of the newer vertical clutch system, lateral clutches tend to be thinner. Many enthusiasts prefer the aesthetics of the lateral clutch as well, due to the visibility of the wheels and their meshing.
Lathe	A machine that rotates a workpiece (a piece of raw material that is getting worked on) on an axis of rotation. The potter's wheel is the most famous type of lathe, but most lathes including those used in watchmaking turn the workpiece on an axis parallel, not perpendicular to the ground. Lathes are ubiquitous tools in watchmaker's workshops as watch dials often have repeating and circular geometric embellishments that require a rotating axis. The rose engine lathe is perhaps the best-known type of lathe in watchmaking due to its ability to produce the desirable guilloché finish.
LB	Lunette Bleue. Rolex nomenclature for a blue bezel.
Leaf Hands	A style of hands distinguished by a curving taper, reaching maximum width at the midpoint of the hand and then coming to a thin tip. The hands resemble thin leaves. Also called by their French name, ‘feuille’ hands. Leaf hands are rarely lumed.
Leap Day	An intercalary date added periodically to certain years to offset the difference between the nominal length of a year in the human Gregorian calendar and the actual length of a solar year (the orbital period of Earth around the Sun). This takes the form of an extra day added to the end of February, which gains a 29th day in a leap year. Also see ‘leap year’.
Leap Year	An intercalary year containing an extra unit of time to offset the difference between the nominal length of a year in the human Gregorian calendar and the actual length of a solar year (the orbital period of Earth around the Sun). This extra unit is a day, or ‘leap day’ in the Gregorian calendar while the Chinese lunisolar calendar and derived systems have a leap month. In the Gregorian calendar, all years divisible by 4 (e.g. 2004) are leap years, unless the year is centurial and thus divisible by 100 (e.g. 2100). However, if the year is also divisible by 400, it is a leap year (e.g. 2000).
Leather Grade	A system of grading the quality of leather. Leather grades are usually determined by tanneries in an alphabetical system. There is no universally agreed standard on leather grades. In the watch world, different cuts and layers of leather used for watch straps are erroneously referred to as grades.
Leather Strap	A strap that is made of leather. Usually composed of two pieces.
Lefty	A nickname for a watch whose crown is on the left side of the case as opposed to the typical right side. Other nicknames include ‘destro’, ‘southpaw’ and ‘LHD’.
Leopard	A nickname for the Rolex Oyster Perpetual Cosmograph Daytona reference 116598SACO, a yellow gold Daytona with round cut diamond hour markers, a bezel set with baguette cut cognac-colored sapphires, end links set with round cut diamonds, and a lacquered dial and leather strap with the eponymous leopard pattern.
Lépine (movement style)	A style of movement where the seconds subdial is mounted at the opposite end the crown on the same axis with the crown stem. This would put the crown at twelve o’clock and the subseconds at six, or the crown at three and the seconds at nine. Not all of Jean-Antoine Lépine’s personal creations were so-called Lépine movements, but the name caught on. Antonymous with ‘Savonette’. Today with the proliferation of wristwatches, the Lépine movement is somewhat rare - virtually all wristwatches have their crown at three and either a central seconds or subseconds at six. However, this arrangement is still common in chronograph wristwatches where the the running seconds is often at nine.
Lépine Caliber	Not to be confused with ‘Lépine (movement style)’. A movement architecture made of a single plate and bridges instead of the bulkier two plates and pillars, and using a wheel train connected to a toothed mainspring barrel instead of the much bulkier fusée-and-chain. These improvements alone made the movement significantly smaller, freeing up room for the balance which was previously mounted on top of all the clockwork. Lépine’s innovations virtually halved the thickness of portable timepieces and changed watch movement design forever. Some experts classify the Lépine calibers into five generations. See ‘Lépine I’ to ‘Lépine V’ for more information.
Lépine I	A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1800 to 1825. Equipped with a double-geared spring limiter or a Geneva stopwork. Used a cylinder escapement.
Lépine II	A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1825 to 1835. Distinguished by a large yoke-shaped bridge that covers half the mainspring barrel. The center wheel cock and center wheel are above the balance wheel. Mostly cylinder escapements with some lever escapements.
Lépine III	A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1830 to 1840. Distinguished by the introduction of a barrel bridge and separation of cocks (one wheel, one cock). Lépine IIIs have radial cock arrangement with few exceptions. Increasing adoption of the lever escapement while cylinder escapement retains dominance. Over the course of the Lépine III the mainspring ratchet click migrates from the center of the barrel bridge to its side.
Lépine IV	A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1835 to 1850. Center wheel is now held by a bridge instead of a cock. The Lépine IVs coincide with the start of mass production and have a great deal of variability in design, finishing, and features.
Lépine V	A generation of Lépine calibers under the classification system made by Lépine expert Adolphe Chapiro. Roughly spans the period from 1850 to 1825. Lépine Vs are easy to identify due to their parallel bridge and cock arrangement, doing away with the radial arrangement of previous generations. Full dominance of lever escapement with the exception of low-end movements with cylinder escapement. Very rare examples have detent escapements. Some later versions of the Lépine V caliber are stem-wound (via crown) instead of key-wound.
Lépine Watch	See ‘open face’. Antonymous with ‘savonnette (watch)’ and ‘hunter watch’.
Lever Escapement	An escapement that utilizes a pivoted lever to engage the balance wheel and train. In most designs the lever is a T-shaped pivoted lever which has a claw-like jewel pallet on each end of the horizontal bar and a swallowtail cut at the end of the vertical bar. The pallets lock and release ('draw') the escape wheel while the swallowtail interacts with a protrusion on the balance wheel called the impulse pin. The lever serves as a perfect mediary for the train and balance as its constant collision with the impulse pin provides impulses to keep the balance running, but the speed at which the impulse pin hits the lever is determined by the preset amplitude of the balance. The lever escapement is known for its combination of accuracy, durability, serviceability, and reliability. It is also a self-starting escapement. Also see 'English lever escapement' and 'Swiss lever escapement'.
Lever-set Pocket Watch	A pocket watch that has a setting lever which must be first engaged to set the time. When engaged the lever allows the crown to move so that the time may be set. When returned to rest the lever prevents the crown from moving. The lever itself is hidden in a cutout under the dial which requires the bezel to be removed and a fingernail or pin to fish the lever out of its resting position. This arrangement makes setting a deliberate action, and is therefore used in high-grade pocket watches that are so accurate that they do not need to be set often anyway. They are thus common in 19th century railroad pocket watches.
LHD	‘Left-hand Drive’. A nickname for a watch whose crown is on the left side of the case as opposed to the typical right side. Other nicknames include ‘destro’, ‘southpaw’ and ‘lefty’.
LIGA	(German) Lithographie, galvanoformung, abformung. ‘Lithography, electroplating, and molding’. In watchmaking, LIGA refers to a manufacturing process that is used to manufacture small components with high precision through photolithography to make molds, and then electroplating/electroforming the final product in galvanic bath.
Light-emitting Diode (LED)	A semiconductor device that emits light when an electric current flows through it, or a display that is made up of such devices. In watchmaking, they are most commonly used for displaying the time in electronic digital watches using seven-segment and/or dot matrix. LEDs emit their own light and thus do not need a backlight to be visible in the dark. LED displays are now less common than LCDs.
Light-powered Movement	A type of quartz movement that is able to replenish its power via exposure to light, especially sunlight. This is achieved through photovoltaic cells on the dial which convert light to electricity, which is then used to charge a capacitor or rechargeable battery.
Ligne (''')	A unit of measurement corresponding to 2.2558mm, or twelfth of a French inch/pouce (27.07mm). Abbreviated with a triple apostrophe ('''). The word is used in its original French form (pronounced [leen]), although 'line' and 'Paris line' are also used. 'Ligne' is still used most commonly to avoid confusion with an English line, which is a twelfth of an English inch and thus slightly shorter than its French cognate. Ligne is an obsolete unit of measurement vestigially used only by the Francophone watchmaking industry.
Lima Timezone	Military timezone name for UTC-11.
Limited Edition	An edition of a watch that is limited to a specific predetermined production number. Compare with 'limited production'.
Limited Production	An edition of a watch that is limited in production but not to a predetermined number of watches. There may be an annual cap on production numbers or a limited period of time the watch may be produced. Compare with 'limited edition'.
Lining	The underside of a watch strap. Many straps such as most fabric straps and rubber straps do have a separate lining. Lining is usually done with a softer material as it makes direct contact with the wrist. It may also use a material better for absorbing sweat.
Liquid Crystal Display (LCD)	An electronically modulated optical device that uses liquid crystals and polarizers to display information. An electric current alters the form of the liquid crystals, either allowing light to pass through or not. In watchmaking, they are most commonly use for displaying the time in electronic digital watches using seven-segment and/or dot matrix. They are capable of displaying higher resolution images than LED displays, but they are not inherently luminescent unlike LEDs. Therefore, they are illuminated by backlights. LCDs are the most common display used in digital wristwatches.
Liquid Escapement	An escapement which utilizes the constant flow of liquid. Usually they were in the form of a container which performed an action once a sufficient amount of water was poured into it. Liquid escapements were essential in clepsydras which were important timepieces before the introduction of mechanical clocks.
LN	Lunette Noire. Rolex nomenclature for a black bezel.
Lobster	A nickname for the Omega Speedsonic references 188.0001 and 388.0800. The name comes from the watches’ case and bracelet which resemble a lobster shell.
Local Time	The time where one is.
Lollipop Hand	A hand style that consists of a thin straight shaft culminating in a circle (usually lumed) and a small tip. Almost exclusively used for seconds hands.
Longcase Clock	A clock style with a tall box body that accommodates a swinging pendulum.
Longines	A watch manufacturer established in Saint-Imier, Switzerland in 1832. Longines is owned by the Swatch Group.
Loop	See 'keeper'.
Lost-wax/Investment Casting	A casting technique where a wax or resin duplicate of the final product is sculpted to make an intricate mold cavity. The wax duplicate is melted away once the mold around it is complete, hence the name ‘lost-wax’. It is the only casting technique that is intricate enough to make components for watches. However, even lost-wax casting is an extremely rare process in watchmaking.
Louis XIV Hands	A style of hands distinguished by a complex scroll pattern towards the base. Louis XIV hands are not lumed.
Loupe	A magnifying device designed to be held or worn close to the eye. While most loupes are simple cylinders with a flared end for the eye, some loupes are designed to be mounted to headgear or glasses. Loupes typically provide 3x to 16x magnification and are used ubiquitously in the horological community by everyone from enthusiasts to watchmakers.
Loupe Holder	A tool that allows a watchmaker to fasten a loupe to the eye, freeing the hands to work on the watch. Loupe holders are often wires but can come in more sophisticated forms.
Low Pressure Resistance	A timepiece's ability to withstand sudden pressure differences between the air inside the case and outside of it. This was particularly a concern for aviators who experienced blown-off crystals after a fast climb because the internal pressure of the watch was still at surface pressure, or one standard atmosphere. This is a less common issue today due to better manufacturing techniques. A similar pressure-related problem still exists for dive watches which surface from saturated diving. See 'helium escape valve' for more.
Lug	An arm-like appendage of a wristwatch that allows it to be attached to a band. Most wristwatches have four lugs in two pairs at the twelve o'clock and six o'clock positions. Each pair of lugs has a removable metal bar in between that allows a band to be attached. See 'spring bar'. Some wristwatches combine the pair of lugs and the bar in between into a single unbroken piece of metal which makes the construction more solid but the variety of compatible bands limited. See 'fixed lug'. Some watches have no dedicated lugs and instead have an integrated band. See 'integrated band'.
Lug Width	The horizontal distance between a pair of lugs. Lug width is necessary for sizing straps or bracelets. Not to be confused with 'lug-to-lug'.
Lug-to-lug	The vertical distance between the twelve o'clock and six o'clock extremities of the watch head, which would normally be the top and bottom lugs. Lug-to-lug measurement is important for understanding the true size of a watch as the wearing experience also depends on the size and shape of the lugs and case profile and not just the more commonly understood case diameter. Not to be confused with 'lug width'.
Lugless Case	A case with no visible lugs. Any lugs on a lugless case are called ‘hidden lugs’. Some lugless cases literally have no lugs, and have a completely unremovable bracelet attached to the case. This is somewhat rare in the modern day as even watches with integrated bracelets have removable bracelets even though their lugs are very unconventional.
Lume	Luminous material which allows the clock to be read under low light conditions. Lume can be found on the hands and/or dial.
Lume Plot	A patch of lume.
Lume Shot	A picture that captures the luminescence of a watch's lume.
LV	Lunette Verte. Rolex nomenclature for a green bezel.
Lyre Lugs	Another name for twisted lugs. It is most often used to describe the twisted lugs of the Omega Speedmaster and similarly-profiled lugs. The name likely comes from how the side profile vaguely resembles a lyre.
Magnetic Resistance	A timepiece's ability to maintain an acceptable level of performance after exposure to a magnetic field. Magnetic resistance is measured in the units of magnetism such as gauss (G), ampere per meter (A/m), and tesla (T). Magnetic resistance is usually achieved with special nonmagnetic components or a magnetically conductive shield for the movement.
Magnifier	An inset magnifying lens on the crystal which increases the legibility of whatever is under it. Magnifiers are usually attached over the date window.
Maillechort	See ‘German silver’.
Main Plate	A large plate which serves as the structural foundation of a movement. Virtually all movement components are anchored to the main plate, either directly or via bridges.
Mainspring	A large spiral torsion spring which stores and releases energy in a mechanical movement, serving as its power source. The mainspring is fixed to an arbor (axle) on one end and the inner wall of the barrel on the other. The natural tendency of the spring to uncoil after being coiled through winding moves the teethed barrel in which it is housed, which in turn moves the gear train. Not to be confused with 'balance spring' or 'hairspring'.
Maltese Cross Mechanism	See ‘Geneva drive’ and ‘Geneva stopwork’. An alternate name for the Geneva drive and stopwork due to the driven wheel’s resemblance to a Maltese cross. The four-armed version almost completely resembles a Maltese cross, but this variant is used more commonly in non-horological clockwork like old cameras and projectors where the rotational energy of a crank must be translated to intermittent motion. In watchmaking the mechanism is mostly used as a stopwork, which means that the driven wheel cannot have even arms - one must always be big enough to set a limit to the number of rotations that a barrel performs. In this instance the even arms still resemble those of a Maltese cross thanks to their V-shaped profiles.
Mantel Clock	A clock style designed to be placed on a mantel.
Manually-wound Movement	A movement which must be wound manually. Synonymous with 'hand-wound' and 'manual wind'. For the vast majority of cases, refers to a type of mechanical movement although there are some exceptions like manually-wound hybrid movements. Also called simply a 'mechanical movement' by some although this term can be technically erroneous and potentially confusing.
Manufacture	(French) Manufacture d'horlogerie. In watchmaking, a 'manufacture' is a watch manufacturer that develops, designs, makes the parts of, assembles, and tests its own watches as opposed to having a significant portion of the aforementioned process done by other companies. Today a similar term 'in-house' has gained more currency, but manufacture refers to the company itself whereas in-house refers to a certain product.
Manufacture d'Horlogerie	(French) A factory which makes its own components. See ‘manufacture’.
Marine Chronometer	An extremely accurate timepiece - usually a clock but sometimes a watch - meant to be used onboard watercraft for navigation, timekeeping, and communication, or a wristwatch that is inspired by the aesthetics of the former. The latter is also commonly referred to as a 'marine watch'. Marine chronometers were kept on a gimbal system mounted inside a protective box in order to keep it level against the rocking motion of a surface vessel. They typically had simple, legible white dials and a power reserve indicator so that the crew could prevent the chronometer from running out of power.
Marine Watch	A category of wristwatch based on the marine chronometer. Sometimes 'marine chronometer' and 'marine watch' mean the same thing. Marine watches supplemented the larger and more accurate marine chronometers that were kept in gimbaled cases. With the advancement of wristwatch accuracy they were impressive timekeepers of their own right. A typical marine watch has big, bold Arabic or Roman numerals in black against a white dial, and sometimes a power reserve indicator reminiscent of those found on marine chronometers.
Marriage Watch	A wristwatch made of components from different watches, especially one that combines the movement of an older watch and a newly-made case. Marriage watches are a popular way of using fine pocket watch movements that would otherwise no longer be used. There is some overlap with the term 'frankenwatch', which carries a highly negative connotation. Generally 'frankenwatch' is used to describe a watch that tries to pass off as genuine and combines anachronistic parts. Even some honest marriage watches which mimic the signature of the movement manufacturer on the dial are seen to border on frankenwatch territory. However, the practice of recasing old movements itself is an old and time-honored tradition.
Masonic Watch	A watch that incorporates design elements of Freemasonry, sometimes designed for Freemasons but also commonly offered as quirky dial options. Most designs feature various Masonic symbols as indices while some feature triangular cases.
Masselotte	(French) See 'inertia block'.
Master Clock	A clock that serves as a time standard and controls other devices dependent on a time signal. The term generally refers to now-antiquated master clocks of the 19th and 20th centuries and not our modern day atomic clocks which send time signals to electronic devices. However, any clock that serves as the supreme timekeeping device of a clock network is technically a master clock. The archetypal master clocks of old were connected via electrical wires to various devices including time card punches, school bells, sirens, and slave clocks in individual classrooms or clock towers. They were often long case pendulum clocks.
Maurice Lacroix	A watch manufacturer established in Zürich, Switzerland in 1975. Maurice Lacroix is privately owned.
Maxi Dial	A dial with enlarged markers, text, or other features. Typically used in Rolex nomenclature for Submariner references 5513, 5512, 5517, and 1680 as well as GMT-Master II references 1675 and 16750. These watches were produced in the 1970s. However, the Maxi configuration is standard for all Rolex watches today that have diver markers.
MB&F	A watch manufacturer established in Geneva, Switzerland in 2005. MB&F is privately owned.
Mechanical Escapement	An escapement which only utilizes purely mechanical components instead of fluid or electricity.
Mechanical Movement	One of the three major types of movement. A movement that uses purely mechanical clockwork, i.e. a mechanism of springs, levers, gears, pulleys, and/or weights to measure and display the time. A mechanical movement has no components that generate or use electricity or magnetism. Additionally, a mechanical movement may refer to a 'hand-wound mechanical movement' or 'manually-wound mechanical movement' which is a mechanical movement whose mainspring must be manually wound as opposed to an 'automatic mechanical movement' which does not require the wearer's intervention to be wound. This usage, while common, is at times technically erroneous and potentially confusing.
Meet-up	A meeting of watch collectors of a certain community, society, club, or for a certain event. Meet-ups are opportunities for enthusiasts to connect with other enthusiasts and try on different watches. Also known as a 'get-together' or 'gtg'.
Memory-in-pixel (MIP)	A type of LCD technology that utilizes a built-in memory for every pixel in the form of static RAM (SRAM). MIP displays are power efficient because the built-in memory in the pixel obviates the need for the processor to constantly refresh the on-screen image - a pixel will remember to stay as is if change is not necessary even without input from the processor. MIP displays also boast superior readability and clarity of image as they place the reflector layer in the middle while conventional displays place it at the bottom. This eliminates the shadow typically seen in most other displays and allows for a flat image that is much clearer and crisper in sunlight.
MEMS	Microelectromechanical systems. A technology in which both electronic and mechanical components make up a microscopic machine. This term is used most in the context of semiconductor production. In watchmaking, MEMS refers to the application of the MEMS fabrication technology of photolithography to the manufacture of watch components. Photolithography utilizes light to lay down a thin protective layer over a substrate so that the uncovered areas can be etched away. This method is ideal for making intricate microscopic components and produces far more precise and smaller products than those made with traditional metalworking techniques such as cutting, milling, stamping, or casting. Thus it can be used to create the smallest and most important components of wristwatches. The technology is most associated with Japanese watchmaker Seiko.
Men's Watch	A watch designed with a male wearer in mind. Modern men's watches typically range from 36mm to 45mm in case diameter.
Mercedes Hand	A style of hour hand that is distinguished by a disc towards the tip with veins in the shape of a three-pointed star that resembles the emblem of Mercedes-Benz. The Mercedes hand can be considered a variation of the cathedral hand. They are always lumed.
Mesh Bracelet	A bracelet with small chain-like links that mesh together like mail. Also called 'Milanese mesh' or 'shark mesh'. The name 'Milanese' comes from the weaving pattern's purported origins in Milan, Italy. 'Shark' mesh likely comes from an Omega advertisement which dubbed the bracelet 'sharkproof'.
METAS	Federal Institute of Metrology. The Swiss national institute for metrology. In watchmaking, METAS most commonly refers to the METAS Master Chronometer certification which certifies the accuracy and precision of timepieces under various conditions.
Mick Jagger	A nickname for the Heuer Carrera reference 1153N chronograph. The name comes from British singer and songwriter Sir Mick Jagger, who famously wore the watch.
Microadjustment	A feature of certain clasps that allow the wearer to adjust the anchor point of the strap to the clasp. Clasps with microadjustment will usually have six or more microadjustment holes with 2mm or 3mm spacing. Microadjustment makes up for the lack of adjustability in clasps compared to buckles. Also see 'quick adjustment'.
Microchip	See 'integrated circuit'.
Micrometer	A unit of length that is one millionth of a meter. More commonly called ‘micron’. In watchmaking, micrometers are most commonly used to measure the thickness of gold plating.
Micron	The non-SI but more popular term for the micrometer. See ‘micrometer’.
Microrotor	A type of oscillating mass in an automatic mechanical movement that is completely horizontally integrated into the movement rather than placed on top of it. The microrotor allows an automatic movement to be significantly thinner due to the elimination of the concentric rotor-weight while providing a better view of the other components of the movement that would otherwise be covered by a large concentric rotor.
Mike Timezone	Military timezone name for UTC-12.
Milanais	(French) Short for 'maille milanaise' Milanese mesh.
Milanese Mesh Bracelet	A style of mesh bracelet with a weave pattern believed to originate in Milan. Known as 'maille milanaise' in French. Milanese meshes tend to have the visible part of the link run parallel with the strap or very slightly diagonal. Also see 'Polish mesh'.
Military Dial	A dial made for or by a military, or one inspired by such dials. Like the term ‘military watch’, the word is loose and does not hold much meaning as is without further elaboration. In the most common sense, the most widely recognized military dials originate from designs finalized during the Vietnam War, where a combination of lumed geometric markers, 12-hour and 24-hour notations, and high-contrast, simple color schemes were set as a uniform standard for watches issued to American troops. Watches with both 12-hour and 24-hour notations are colloquially referred to as military dials.
Military Time	A convention of timekeeping used by the military. While not all militaries use the same convention, timekeeping is somewhat uniform around the world. Military time uses the 24-hour notation to avoid ambiguity, typically with no colon (:) in the middle to separate the hours and minutes, and may be accompanied with an alphabetical designation to denote the time zone.
Military Watch	A catch-all term for all watches associated with the armed forces, paramilitaries, and private military organizations. In the narrowest sense it refers to 'issued watches' - watches issued by the military itself - and watches designed for use by military personnel. In a broader sense it may refer to any watch used extensively by military personnel regardless of original intent. Naturally military watches may refer to field watches, dive watches, pilot's watches, and any other category of watches that various types of soldiers may find useful.
Millerighe	(Italian) ‘Thousand lines’. A nickname for the first style of screw-down pushers used in Rolex Daytonas, namely on reference 6240.
Milling	A metalworking technique that involves the machine-cutting of a metal workpiece with a milling cutter into a desired shape. Milling is a complex and precise technique that works with a solid metal workpiece. Hence, it is the most expensive but creates the heaviest, most durable, and most intricate product. Milling is appropriate for machining complex components such as cases or solid components such as crowns. On more costly timepieces, every metal component including the bracelet links and clasp are milled.
Milsub	A nickname for the Rolex Oyster Perpetual Submariner references A/6538, 5513, 5517, and 5513/5517 that were modified for and issued by the Ministry of Defense of the United Kingdom. The name is a portmanteau of 'military' and 'Submariner'. Of these, the A/6538 is sometimes separated from the latter three as it was a low-production prototype that many do not regard as a full-fledged Milsub. The latter three Milsubs share certain modifications such as a larger and grippier fully-graduated bezel, tritium lume, fixed lugs, sword hands, and military markings on the caseback.
Mineral Glass	A silicate glass that is heat and chemical treated for increased hardness. Untreated mineral glass rates around 5 on the Mohs hardness scale while treated glass rates up to 7. Mineral glass stands in the middle of the road in the watch crystal spectrum. It is softer than sapphire and harder than acrylic, heavier than acrylic but lighter than sapphire, and more expensive than acrylic but cheaper than sapphire. Unlike acrylic, mineral glass shatters on strong impact much like sapphire and cannot be polished.
Mini Dial (Rolex)	See ‘radial dial (Rolex)’.
Mint	A condition level that indicates that the timepiece is the exact condition it left the factory. It may have been taken out of its packaging and even worn a couple of times, but there must be no change in condition from its original condition. A common but erroneous understanding prevalent in the watch collecting community is that 'mint' means 'very good condition'. Mint watches must be flawless regardless of circumstance where as any other condition level may factor in the age of the watch.
Minute Hand	The hand that points to the minute. Makes a full rotation every hour.
Minute Rack	A rack which interacts with the minute snail and the hammer trip of the treble hammer. It is lined with fourteen teeth, one for each minute between full quarters.
Minute Recording Jumper/Pawl/Click	A component of a chronograph mechanism that applies constant pressure to the minute recording wheel so that the chronograph minute hand advances in the desired manner and so that bumps and knocks do not throw off the position of the chronograph minute hand.
Minute Recording Wheel	A component of a chronograph which moves the chronograph minute hand.
Minute Repeater	A striking complication that repeats the hours, quarters, and minutes since every quarter on demand. Typically the hours are sounded with a bass note, the minutes with a treble note, and the quarter with one bass and one treble. For example, 02:47 would be "dong, dong, ding-dong, ding-dong, ding-dong, ding, ding".
Minute Snail	A snail cam which transmits information on the current minutes to the minute feeler so that a repeater can announce the current minute. The minute snail is in the shape of a four-pronged pinwheel/curved swastika, each arm (representing a quarter) with fourteen levels cut out like a sawtooth.
Minute Wheel	A component of the motion work that serves as the reduction gear for the hour hand. It meshes with the cannon pinion and is designed to rotate once every twelve hours, which is usually achieved by having a much larger circumference. The minute wheel’s coaxial pinion meshes with the hour wheel. Unlike what may be inferred from the name, the minute wheel does not control the minute hand. Therefore it should not be confused with the second wheel, which is sometimes called the ‘minute’ or ‘minutes’ wheel because it is responsible for turning the minute hand.
Mirror Finish	See 'mirror polish'.
Mirror Polish	See 'black polish'. Generally mirror polish is also seen as a somewhat less fine level of finishing than black polish, although the definitions are not clear. In many cases they are used interchangeably.
Mirror Track	A track or chapter ring that has a shiny, mirror-like finish when the rest of the dial is a different texture.
Miscellaneous Swiss	A designation for a timepiece with Swiss origins but no other information regarding the manufacturer or brand.
Mitsukoshi	A nickname for the Omega Speedmaster Professional reference 3570.31.00 limited edition specially made for the Mitsukoshi department store in Japan.
Mod	An aftermarket modification of a watch. The term typically refers to modifications done by switching certain OEM parts for third-party ones instead of more laborious and technical customization jobs done by personalization/customization specialists. However, any modification can technically be considered a mod. In most cases including the most expensive mods, the movement is left untouched. Some modders do tweak the movement, usually by skeletonizing the plates and bridges for visual effect.
Modular Chronograph	A chronograph mechanism that is designed as a separate mechanism that can be attached to a movement as opposed to one that is a native part of it. Antonymous with ‘integrated chronograph’. Modular chronographs are popular options for companies that do not wish to invest resources on developing an integrated mechanism. As an integrated chronograph is sold as a module, the mechanism is usually bunched up under a single plate or bridge and has its own mainplate. This may sometimes prove trickier or easier for servicing depending on the issue. The chrono hands on modular chronographs also typically tend to jump as if startled on operation. Nonetheless, modular chronographs vary greatly in quality and some boast excellent features.
Module (mechanical)	An independent assembly of components meant to perform a specific function, especially as an add-on to a preexisting movement. Modules are typically designed by specialty manufacturers for complicated mechanisms such as chronographs that are difficult and costly to develop in-house. A complication or movement can be described as 'modular' if it utilizes a module. Not to be confused with 'module (quartz)'.
Module (quartz)	A quartz movement. Not to be confused with 'module (mechanical)'.
Mohawk	A nickname for the Seiko SRP585, SRP587, SRP589 and other similar divers with a raised twenty-minute section on the rotating bezel that resembles a mohawk.
Momiji	(Japanese) A nickname for the Grand Seiko reference SBGH269 which has a red dial reminiscent of autumn leaves. 'Momiji' is Japanese for 'red leaves', 'autumn colors', or the Japanese maple.
Monaco (Seiko)	A nickname for the Seiko 7016 and 7018 series automatic flyback chronographs with a rectangular case reminiscent of the iconic Heuer Monaco.
Mono-rattrapante	A chronograph that has a chronograph seconds hand that can be stopped while the chronograph is running and then released to catch up to the position corresponding to the current elapsed time. For example, if the chronograph was stopped at 15 seconds and held for thirty seconds, releasing the pusher would launch the chronograph seconds hand to the 45-second position to resume timing. It is essentially a simpler version of the split-seconds chronograph/rattrapante with the same ‘catch-up’ function but with only one chronograph seconds hand and no dedicated split pusher. The mono-rattrapante is an extremely rare complication.
Monobloc Case	A case that is fashioned out of a single solid block of metal instead of assembled from parts. A monobloc case lacks a separate caseback. This means that movement maintenance can only be performed by completely removing the movement through the front opening. However, monobloc cases offer better protection against water and dust in theory as they eliminate a potential weakness of the case. Some monobloc cases are engineered to keep out even helium atoms, thus eliminating the need for helium escape valves. With modern technology monobloc cases are practically a stylistic choice as threaded casebacks are more than sufficient.
Monoblocco	(Italian) Monobloc. A nickname for the Rolex references 3525 and 4500. The name refers to the fact that the bezel, lugs, and case are all milled out of a single block of metal, as opposed to many other watches where the lugs are attached later and the bezel is removable.
Monopusher Chronograph	A chronograph with only one pusher for start/stop and reset as opposed to the now-conventional assortment with two pushers. As there is only one pusher, a monopusher chronograph can only operate linearly - the order of operation will always be start, stop, and reset, with no possibility of resuming timing after the chronograph is stopped unlike in a two-pusher chronograph which can be stopped and resumed an unlimited number of times. Monopushers were the standard until the introduction of the two-pusher chronograph which is superior in usability and practicality. However, monopushers are still quite common today as they offer a simpler look and can be integrated into the crown. They also have the advantage of being impossible to fumble because one cannot press the pushers in a wrong order.
Monster	A nickname for the Seiko SKX779 diver and the various divers that take after it. The name comes from the aggressive bezel, bold and teeth-like indices, and large hands.
Monte Carlo	A nickname for the Tudor Oysterdate references 7149/0, 7159/0, and 7169/0. The name is a reference to the historic Monte Carlo casino, as the unique design of the watch is reminiscent of a roulette wheel.
Montre	(French) A watch or clock.
Montre-école	(French) School watch.
Montreal	A nickname for the Omega Seamaster Chrono-Quartz reference ST396.0839. The name comes from the both the circumstances of its release and composition of the display. The watch was created for the 1976 Montreal Olympics and resembles the event’s main analog-digital scoreboard. The same watch is also called the ‘Olympic’ and the ‘Albatross’.
Moon Hands	A style of hands distinguished by a ring towards the tip. The more popular ‘Breguet hands’ are considered a style of moon hands, but moon hands typically have an untapered, straight body and usually have long pointer tips as apposed to the triangular tips on Breguet hands. The two terms can be used interchangeably. Moon hands are not lumed.
Moon Phase	A calendar complication that displays the shape of the moon for a given night. It looks similar to, but should not be confused with, the day-night complication.
Moonwatch	A nickname for the Omega Speedmaster Professional reference 105.012 and all Speedmaster Professional chronographs that follow in its pattern. The ref.105.012 was issued to the astronauts of Apollo XI and in 1969 was the first timepiece worn on the lunar surface. Since the success of the lunar mission, Omega has always kept a Speedmaster Professional in their product lineup that preserves the old-school formula of the Speedmasters of the time: a manually-wound, triple-register, 12-hour, no-date, stainless steel chronograph with an option for a solid caseback and hesalite crystal. These subsequent generations of the Speedmaster Professional are all called Moonwatches and contrast with other Speedmasters that incorporate the newer designs, materials, and complications of their time.
Morpho	A nickname for the Seiko Superior 3883-7000 which has an textured and mottled iridescent blue dial. The nickname is likely a reference to a genus of butterflies which is known for having many species with metallic blue or green wings. The watch is also called ‘Butterfly’ and ‘Peacock’.
Motion Work	A mechanism that turns the hour hand with the minute hand via a reduction drive. As the hour hand needs to turn twelve times slower than the minute hand, a 12:1 gear reduction is necessary. The motion work consists of the cannon pinion, minute wheel, and hour wheel.
Motor	A machine that converts electrical energy to mechanical energy. In watchmaking, motors usually refer to the motors in analog electronic watches which move the hands and other mobile components of the watch. There are largely two types of motors: the step motor and non-step motor.
Movado	A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1881 and now headquartered in Paramus, USA. Movado is owned by the Movado Group.
Movement	The mechanism of a timepiece which measures and displays the time. Also called a 'caliber' especially when referring to a specific movement. In electronic watches the movement is sometimes called the 'module'.
Movement Holder	A tool that holds a movement that is removed from its case. Movement holders can look like adjustable vices or come in dimensions dedicated to a specific movement.
Mt. Iwate	A nickname for the Grand Seiko reference SBGJ001/021 GMT and all other watches with the same 'Mt. Iwate' dial texture. The dial texture was inspired by and gets its name from the ridges of Mt. Iwate, a snow-capped stratovolcano located near Grand Seiko's Shizukuishi Watch Studio in Iwate Prefecture, Japan.
Mühle-Glashütte	A watch manufacturer established in Glashütte, Germany in 1869. Mühle-Glashütte is privately owned.
Mumbai Special	A derisive name for fake watches assembled in India, especially Seiko 5s.
Mute/Silence	A switch, button, or slide which disarms the striking complication, preventing it from making any sounds. It may also be used to silence an ongoing chime.
Nato Strap	A style of one-piece strap that is constructed using two connected pieces. Also called a NATO strap, it is usually made of a fabric like nylon. The long piece, which is sewn and glued to the top of the short piece, is pulled through the watch's lugs and then through a metal keeper fixed at the end of the short piece. The remaining strap length is tucked and organized with two fixed keepers. This effectively fastens the watch not to the wrist but to the strap itself. If a spring bar fails due to high impact or abrasion, the watch head will dangle from the strap instead of coming off the wrist like it would with a two-piece strap. Nato straps were first developed for the military but are now adored by others who would need a cheap and failsafe strap like surfers, divers, outdoorsmen, and anyone who appreciates the aesthetic. Also see 'zulu strap', 'nato zulu strap', and 'RAF strap'.
Nato Zulu/Five Ring Zulu Strap	A style of one-piece strap that is constructed using two connected pieces. It is usually made of a fabric like nylon. Like the name implies, the nato zulu strap is a hybrid of the nato and zulu straps. It uses the two-piece construction of the nato strap while using zulu-style hardware. Unlike a zulu strap which has three hoops/rings to organize the unused length of the strap, a nato zulu has two additional rings in lieu of the nato's fixed keeper at the end of the short piece. This is why it is also called the five ring zulu. The advantages of the nato zulu strap are primarily reduced pressure on the strip bars and its variable strap length. The long piece can be pulled through the two extra hoops twice to shorten the strap, and just once to reveal its full length. This is useful when wearing the watch over the cuff. Also see 'nato strap' and 'zulu strap'.
Negative Display	An electronic digital display (LCD or MIP) where the assets are presented in a lighter color than the background.
Neo-vintage	In watchmaking, 'neo-vintage' refers to an object that is approaching vintage status. As of the 2020s, neo-vintage refers to watches produced in the 1990s and 2000s.
New Old Stock (NOS)	A timepiece is considered new old stock when it is both (i) a reference that is no longer in production (old stock), and (ii) in mint condition (new). The term is used mostly for vintage timepieces but any timepiece regardless of production year can be new old stock as long as it is no longer in production.
NFS	‘Not For Sale’. Watch collecting social media abbreviation to indicate that a watch is not available for purchase. Also see ‘FS’.
Nickname	In watchmaking, a nickname is a colloquial, usually-unofficial monicker given to a watch that captures a distinct quality. It is different but sometimes related to the official name of a watch. Watch manufacturers and certain movements may also have nicknames.
Nina Rindt	A nickname for Universal Genève Compax reference 885103 chronograph, and sometimes the similar ref.885105, ref. 885107, and ref.885108. The more famous panda dial ref.885103/1 is known as the Nina Rindt as it was worn prominently by fashion icon and model Nina Rindt to her husband Jochen Rindt’s races. (Her husband wore a Heuer Autavia, see ‘Jochen Rindt’) She wore the watch on a leather cuff. The reverse panda ref.885103/2 is called the ‘Evil Nina’. References 885107 and 885108 are called ‘Exotic Nina’ due to their exotic dials.
Nipple Dial	A dial with applied conical indices topped with lume. The applied indices somewhat resemble nipples.
Nivada Grenchen	A watch manufacturer established in Grenchen, Switzerland in 1926 and revived in 2018. Nivada Grenchen is privately owned.
Nivarox (alloy)	A nickel iron alloy commonly used for hairsprings, produced by a company of the same name. The name stands for 'nicht variabel oxydfest', German for 'non-variable, non-oxidizing'.
Nivarox (company)	A company that produces watch components, especially components made of its proprietary alloy. The name stands for 'nicht variabel oxydfest', German for 'non-variable, non-oxidizing'. Nivarox is owned by the Swatch Group.
Nomos	A watch manufacturer established in Glashütte, Germany in 1990. Nomos is privately owned.
Non-step/Sweep Motor	A motor that does not step bur rather moves in a continuous motion. One of the two types of motor. Sweep motors are less common in quartz watches because of their large energy consumption compared to step motors. Timepieces with sweep motors can be identified with unbroken movement of the seconds hand.
Noon Gun	A signal gun which fires at noon.
November Timezone	Military timezone name for UTC+1 or UTC-13.
Nubuck	A type of leather. Nubuck is a top-grain leather that is buffed to a smooth, velvety finish much like suede/split grain leather. As it is a top-grain leather, nubuck is far more durable and water resistant than suede. However it is also more expensive.
Numeral	A numerical marking on a dial which indicates the hours. A type of index, although an index usually refers to a non-numerical hour marker.
NWA	Watch collecting social media lingo meaning 'New Watch Alert'. Accompanied by a photo of a newly acquired watch.
O-ring	See 'gasket'.
Obelisk Hands	A style of hands distinguished by a broad base tapering gently to a thin neck with a triangular tip. The obelisk hand resembles the namesake obelisk in architecture. It is sometimes alternatively spelled ‘obélisque’ from French.
Observatory	An installation and facility built for the observation of various events. In the watch world, the term refers to an astronomical observatory which surveys and studies the movement of celestial objects. These observatories were also involved in timekeeping as human time relies on the movements of the Earth, Sun, Moon, and sometimes stars. These observatories often held accuracy competitions which many watch manufacturers used to test the accuracy of their movements. Also see ‘observatory chronometer’.
Observatory Chronometer	A chronometer - an extremely precise timepiece - whose accuracy has been certified by an astronomical observatory. It does not mean that it is a timepiece used by an observatory, unlike in other uses of the word ‘chronometer’ like in ‘marine chronometer’ and ‘railroad chronometer’. It is commonly regarded as the most prestigious appellation a timepiece can be awarded. Observatory chronometer movement serial numbers are individually recorded and issued a ‘Bulletin de Marche’, or a certification of accuracy.
OCC Caliber	A Rolex caliber that is officially certified by a third-party testing organization such as an observatory. They are called OCC calibers because they are accompanied with the dial text ‘Officially Certified Chronometer’. They replaced the ‘Chronometer’ text in the late 1930s, which signified that the movements were tested in-house and not by an official body. The OCC calibers were phased out by the so-called SCOC calibers starting from 1957.
OCC Dial	In a broad sense, an OCC dial is any dial that has the dial text ‘Officially Certified Chronometer’ (O.C.C.) on it, which was retired in favor of the still-used ‘Superlative Chronometer Officially Certified’ (S.C.O.C.). This marked the existence of either the older OCC caliber or the newer SCOC caliber. In a narrow sense, it refers to the dials on the early examples of the reference 1675 GMT-Master that still carried the OCC designation of the previous ref.6542 despite some of them having non-OCC calibers. The ref.1675 eventually also adopted the SCOC designation in 1960, a year after the reference was introduced. See ‘OCC caliber’ and ‘SCOC caliber’ for more information on the difference.
Octagonal Case	A case shape distinguished by an octagonal profile. Not to be confused with an octagonal bezel that is fitted to a round case.
Octopussy	A nickname for several Rolex Oyster Perpetual Day-Date references that have gem-set bracelets with round cut gems on the outer links and baguette cut gems on the center links. This setting makes the bracelet resemble the underside of an octopus’ tentacle. The name ‘Octopussy’ is a reference to a character in a Bond film who has nothing to do with the watch save for the octopus connection.
OEM	Original Equipment Manufacturer. A production facility that is officially contracted by a watch brand or company to produce components and/or assemble the final product. It may also refer to production facilities directly owned and managed by the company itself. For most intents and purposes, OEM can be used interchangeably with ‘factory’. An OEM part that is available for purchase means that it was produced by the same factory that makes the parts for new watches. However, factory refers to the way that the watch is when it left the production facility while OEM simply refers to the origin of a part. Thus, a watch that is fitted with replacement OEM parts is not necessarily factory especially if the installation was not done by the factory.
Officer Caseback	An alternative name for a hinged caseback. The name 'officer' comes from the officer style of wristwatches, which often features a hinged caseback. Military officers were among the first people to adopt wristwatches, which in their incipiency largely consisted of small size pocket or pendant watches modified to accept a strap. As a hinged caseback is a necessary feature in many of these pocket and pendant watches in order to protect the winding keyhole, the hinged caseback became associated with officers' wristwatches. Also see 'hinged caseback', 'hunter caseback', 'hinged dust cover', and 'half hunter caseback'.
Oil-filling	The act of filling the internals of a watch, particularly the space between the crystal and dial with transparent oil. The primary purpose of doing this is to eliminate parallax caused by refraction of light, especially when underwater. This is because the refraction index of oil is similar to that of a crystal. An additional benefit is added water resistance as the oil provides additional support to the crystal against external water pressure. Some watches are oil-filled for stylistic purposes as similar refraction index of crystal and oil makes the dial to appear pasted on the crystal. With very few exceptions, all oil-filled watches are quartz as mechanical movements cannot operate when submerged in oil. The few exceptions employ a completely sealed-off air-filled chamber for the mechanical movement.
Olongapo Bracelet	A cuff-style bracelet consisting two curved bands of metal joined by a clasp of some sort, usually a simple hook or single-fold. The name comes from the city of Olongapo in the Philippines which, along with other municipalities in Subic Bay, was home to the United States Navy. The Olongapo bracelets were made by local craftsmen and often featured emblems of the USN, Seventh Fleet, and/or various qualification badges like jump wings or diver insignias. The bracelets replaced factory bracelets or the issued straps and became popular souvenirs for sailors.
Olympic (Omega)	A nickname for the Omega Seamaster Chrono-Quartz reference ST396.0839. The name comes from the both the circumstances of its release and composition of the display. The watch was created for the 1976 Montreal Olympics and resembles the event’s main analog-digital scoreboard. The same watch is also called the ‘Montreal’ and the ‘Albatross’.
OM Dial	A dial with the letters 'OM' printed near the five and seven o'clock markers. OM stands for 'or massif', French for 'solid gold'. These marks were printed on Omega watches whose dials were made of solid gold. Also see 'sigma dial'.
Oman Dial	A dial ordered by and bearing a mark of the Sultanate of Oman. They appear on watches from Rolex, Patek Philippe, Audemars Piguet, Breitling, and others. There are largely two types of Oman dials: the Khanjar and Qaboos. The Khanjar dials feature the Omani Khanjar, a curved dagger that serves as the national emblem. The Qaboos dials feature the signature of Sultan Qaboos bin Said, an important watch enthusiast who commissioned these special order watches as state gifts. Watches with Oman dials were ordered through British retailer Asprey and later Omani retailers Al Qurum and Khimji Ramdas. As per convention at the time, many watches bear retailer signatures, but engraved on the caseback to make room for the special prints on the dial. In rare occasions, these special order watches bore only a caseback engraving or none at all (instead signed on paperwork and box).
Omega	A watch manufacturer established in La Chaux-de-Fonds, Switzerland in 1848 and now headquartered in Biel/Bienne, Switzerland. Omega is owned by the Swatch Group.
On Command	In a striking watch, a strike on command is activated at the wearer's command via a mechanical actuator such as a slide or pusher. Antonymous with 'in passing'. Examples of strikes on command are repeater watches.
One-hander	A clock with one hand. A one-handed clock only has an hour hand. Typically the dial has more pronounced graduation to enhance legibility.
One-watch Collection	A collection consisting of only one watch, or a watch that is so versatile that it constitutes a collection on its own. As an average modern person’s lifestyle typically cycles through work, afterwork leisure, vacation, and exercise, a one-watch collection should be capable of covering most of those bases. Also see ‘GADA’.
Onion Crown	A style of crown distinguished by deep fluting and a bulbous profile resembling an onion. Onion crowns are usually oversized and easy to grip as they were designed for aviators who were operating the crown with gloved hands. Therefore onion crowns are a common feature of pilot's watches. Often confused with the similar 'conical crown', which looks similar and serves the same purpose.
Onyx Dial	A dial made of onyx. Famously used on the Rolex Day-Date reference 18238.
Open Caseback	See 'exhibition caseback'.
Open Face	A pocket watch with no metal cover protecting the crystal. Outside the watch collecting community the term is synonymous with 'openworked'. Many of legendary watchmaker Jean-Antoine Lépine’s creations were open faced. Thus, open faced pocket watches are sometimes called Lépine watches. Antonymous with ‘savonnette (watch)’ and ‘hunter watch’.
Open Heart	A dial style that showcases the balance wheel through a cutout.
Openwork	An openworked watch exposes the movement through the front of the watch, either through a cutout in the dial or by having no dial at all.
Operating Lever Spring	A component of a chronograph mechanism which applies constant pressure to the operating/column wheel lever.
Operating/Column Wheel Lever	A component of a chronograph mechanism which pulls on the operating lever click/column wheel hook, which in turn pulls on the ratchet teeth of the column wheel to advance it. It can be identified as a long lever that runs along the periphery of the movement.
Organ	A group of components that collectively perform a function.
Oris	A watch manufacturer established in Hölstein, Switzerland in 1904. Oris is privately owned.
Oscar Timezone	Military timezone name for UTC+2.
Oscillating Mass	In watchmaking, an oscillating mass moves within a set area to store potential energy in a movement's power source. In a mechanical and some hybrid movements the oscillating mass stores potential mechanical energy in a mainspring while in certain electronic movements it stores potential electrical energy in a capacitor. Oscillating masses are often referred to as rotors or rotor-weights and come in many shapes and configurations, including centrally mounted rotors, bumpers, microrotors, and peripheral rotors.
Oscillating/Rocking Pinion	A chronograph mechanism and the eponymous component of a chronograph mechanism that relies on a moving arbor with one pinion on each side which acts as the clutch mechanism for a watch’s drivetrain and chronograph. Essentially a simple and ultra-compact version of the lateral clutch, the oscillating pinion meshes with the fourth wheel at the bottom pinion until the chronograph starts, when it is moved to also mesh with the chrono runner at the top pinion. The arbor is mounted on a rocker lever and capped with a pivot jewel, which makes it virtually invisible. It shares several of the wear-related shortcomings of the lateral clutch without the visual spectacle. However, the oscillating pinion’s direct connection and compact size preserve amplitude and reduce both potential lag or wobble seen when three large wheels on a lateral clutch are trying to mesh. It is loved for its compactness and is thus common in chronographs that have other features or ultra-thin chronographs.
Oscillation	A back-and-forth movement at a regular speed. It is usually used to describe the actions of the timekeeping organ of a timepiece. In a mechanical movement, one clockwise and counterclockwise spin form a single oscillation. In a quartz movement, a vibration of the quartz crystal oscillator is a single oscillation.
Outer Link	The link that is at the margin of a bracelet.
Outsourced	Executed by an external company. The term has no clear standard as to what it means. In common usage, 'outsourced' is largely synonymous with 'third party' and 'ébauche'. However, the latter term can only be used for movements.
Oval Case (case shape)	A case shape distinguished by a vertically long oval profile.
Oval Case (storage)	A form of watch storage that utilizes a cylindrical hard shell that follows the contours of a watch strapped to a cushion. A typical oval case has a hard but slightly bendy velvet-lined skeleton and hard cushions. The cushions are often attached to the walls of the skeleton with rivet buttons. An oval case cannot accommodate so many watches as they must be lined horizontally in one row. However, it offers a secure fit as the cushions can be fastened to the walls unlike many other cases.
Over the Cuff	The act of wearing a wristwatch over the cuff of an article of clothing. See 'watch over cuff'.
Overbanking	A phenomenon where the impulse jewel escapes its optimal range of motion and lies outside the pallet fork horns. As the impulse jewel often strikes the outside of the pallet fork immediately after overbanking, it is also known as ‘knocking’. Overbanking stops the watch from working. That is because the overbanked impulse jewel can no longer interact with the pallet fork, which means that the escapement cannot be unlocked. The balance can no longer receive impulses from the escapement either, which means that it will no longer swing. Overbanking is often a result of improper timing - a premature unlocking of the pallet fork.
Overhaul	A type of service where the watch is completely disassembled for inspection and cleaning. Overhauls are recommended once every decade for mechanical watches for optimal operation. Consumable parts like gaskets may be replaced as standard, while other parts may be replaced upon the client's request.
Oversize(d) Watch	A watch whose case/dial diameter exceeds conventional size. Oversize watches were generally more legible and could accommodate more functions than their normally-sized counterparts. Various professionals including aviators, navigators, engineers, scientists, and astronomers have used oversize watches throughout history. Today oversize watches are often a fashion choice.
Oversized Crown	A crown that is large proportionate to the case size. While sometimes an aesthetic choice, oversized crowns are commonly seen on tool watches especially those that are meant to be operated with gloved hands.
Overwinding	The act of winding a mainspring beyond an acceptable limit. The threshold for overwinding depends on context. In some, more technical instances, overwinding refers to the complete winding of the mainspring beyond its optimal torque region, where it will suddenly produce a disproportionate torque output. In common parlance, overwinding refers to the winding of a watch beyond the spring’s mechanical limit, i.e. after the mainspring is completely wound and cannot move (tighten) any further. Overwinding a watch can cause a great deal of damage to the clockwork. Attempting to wind the watch beyond its mechanical limit will break the keyless works. Many watches have overwinding prevention mechanisms in place.
Overwinding Prevention Mechanism	A mechanism that prevents overwinding a watch’s mainspring beyond its mechanical limit. This mechanism is mandatory in all automatic watches as without it, the movements of the wrist will overwind and damage the watch in a short time. This mechanism exists in many forms, including a bridle at the end of a mainspring (also called a slipping spring) or a slipping clutch.
Ovettone	(Italian) Large egg. A nickname for the Rolex Bubbleback, which has a protruding caseback that resembles an egg. Also see 'Bubbleback'.
Owl	A nickname for a dial with two large sub-registers at three and nine o'clock.
Oyster	In watchmaking, 'oyster' is related to various trademarks held by Rolex as well as imitations of these products. An Oyster case is a waterproof/water resistant case first released in 1926 and continuously updated to this day. The Rolex Oyster was the watch that was equipped with the aforementioned case. The Oyster bracelet is a three-link bracelet made by Gay Frères and paired with watches of the Oyster Perpetual family.
Oyster Bracelet	A three-link bracelet with wide, long, and flat links and single-fold clasp produced by Rolex. The original bracelets were made for Rolex by Gay Frères. The Oyster bracelet comes on virtually all Rolex models from the Datejust to the Sea-Dweller. Due to its iconic status the bracelet has been widely mimicked and copied, setting the standard for virtually all sporty watch bracelets today.
Oyster Sotto	(Italian) Oyster ‘under’. A nickname for the Rolex Oyster Cosmograph Daytona reference 6263 with a reverse panda Paul Newman dial whose Oyster signature is under the Cosmograph signature. Normally the Oyster signature is above the Cosmograph signature. These exceedingly rare watches are also called ‘RCO’ Daytonas because the signature reads ‘Rolex, Cosmograph, Oyster’ from top to bottom.
Oysterflex	A rubberclad bracelet produced by Rolex. While the Oysterflex looks like a strap, each piece is constructed of a metal blade clad in elastomer. Hence, it is a bracelet or a metal-reinforced rubber strap.
p.m.	(Latin) Post meridiem. The last twelve hours of the day in a 12-hour clock. Starts at 12 p.m. (midday/noon) and ends at 11:59 p.m.
Padding	Material inside a strap that gives it more structure and body. Padded straps may contribute to the longevity of the strap and reduce its risk of tearing. Many people also prefer the aesthetic look of padded straps. However, padding negatively affects pliability and may take away from wearing comfort.
Paddle Hands	A style of hands that resemble cricket paddles. Some paddle hands have a pointer tip at the end as the broad tip of the paddle hand makes it difficult to read the exact time. Paddle hands are typically lumed.
Padellone	(Italian) A nickname for the Patek Philippe reference 3448, 3450 automatic perpetual calendar with moon phase and the Rolex reference 8171 triple calendar with moon phase. The nickname comes from the Italian word for 'large frying pan' and is a reference to the large, oversized (for the time) dial. The Patek and Rolex Padellones are not related but do look similar.
Painted	A component is painted when it is painted onto the dial with a brush. Usually it implies painting done by hand.
Palace Decoration Bracelet	An ultra-thin and intricately-engraved precious metal bracelet made by Gay Frères for Piaget. The bracelet is composed of multiple tiny E-shaped links that have a flexibility and appearance similar to mesh.
Palladium (Pd)	An element used in the manufacture of watches. Abbreviated Pd. Palladium is naturally white in color and not so dense. The metal is most commonly used in white gold alloys as the source of the alloy's white color. Palladium-mixed alloys rarely need rhodium plating to make the metal appear white. However, palladium is rarely used as a standalone case material. Palladium shares many qualities with platinum (Pt), and is in the platinum-group metals alongside other white metals used in watchmaking such as platinum, rhodium, iridium, and ruthenium.
Pallet Arbor	The arbor which anchors the pallet fork and allows it to pivot.
Pallet Fork/Lever	A component of the escapement that serves to lock and release the escape wheel one tooth at a time at the pace dictated by the balance. The component may equally be referred to as a fork or lever as it is a lever with a forked end. A typical pallet fork is a T-shaped lever with a claw-like jewel tooth called a pallet jewel on each end (called the entry and exit pallets) of the horizontal bar and a fork at the end of the vertical bar. As the fork is knocked around by a protrusion in the balance called the impulse pin via the horns of the fork, it pivots on the pallet arbor. The pivoting motion causes the entry pallet to open and allow the escape wheel to turn once, after which it is stopped by the exit pallet as it moves into the closed position. When the fork is knocked again, it pivots once more and opens the exit pallet, allowing the escape wheel to turn one position again after which it is halted by the entry pallet.
Panda (Seiko)	A nickname for the Seiko reference 6138-8020 automatic chronograph which has a typical panda dial consisting of a white dial and gray sub-registers. However, the 6138-8020 variant that comes with an all-black dial is still called 'Panda' despite not having a panda dial.
Panda Dial	A white dial with black sub-registers.
Panerai	A watch manufacturer established in Florence, Italy in 1860 and now headquartered in Geneva, Switzerland. Panerai is owned by Richemont.
Paneristi	A fan, collector, or aficionado of the watch manufacturer Panerai.
Papa Timezone	Military timezone name for UTC+3.
Papers	The relevant documentation unique to a watch which must show at least the reference number and serial number of the watch, if not also the unique serial number of every marked component (such as a movement or bracelet). Papers may also include a chronometer/accuracy certification, instruction manual, and service-related documents.
Passing Hollow	A circular cutout on the roller which provides space for the guard dart of the pallet fork to pass through. Together with the guard dart, the passing hollow is a safety mechanism that prevents overbanking. In a single roller arrangement, the passing hollow is cut out on the rim of the roller. In a double roller arrangement, it is cut out on the safety roller which is hidden below the larger impulse roller.
Patek Philippe	A watch manufacturer established in Geneva, Switzerland in 1839 and now headquartered in Plan-les-Ouates, Switzerland. Abbreviated ‘PP’. Patek Philippe is privately owned.
Patina	In watchmaking, 'patina' is used to describe any sort of natural change to a surface's color, texture, or other properties that arises from exposure to oxygen, constant wear, and/or time. Virtually any part of a watch can become patinated including plastic crystals and even leather straps unless it is made of materials like ceramic or synthetic sapphire. While some view patina as glorified imperfections, beautifully patinated timepieces can be highly desirable. Moreover, patina is a useful clue for ascertaining the authenticity of a timepiece or individual parts.
Patrizzi	A nickname for the early series Rolex Oyster Perpetual Cosmograph Daytona reference 16520 which had incomplete varnish application over the dial, resulting in oxidation in the sub-register tracks. The oxidation resulted in a rich, light brown cream color which many collectors appreciate. The name takes after Osvaldo Patrizzi, founder of watch auction house Antiquorum, who publicized this phenomenon. This varnish issue was subsequently corrected.
Paul Newman	A nickname for the Rolex Cosmograph Daytona references 6239, 6241, 6262, 6263, 6264, and 6265 that sport the so-called 'exotic dial'. The exotic dial is distinguished by a somewhat empty-looking dial due to a contrasting chapter ring, short hour markers that are tucked into the chapter ring, red 'Daytona' text above the hour sub-register, and sub-registers with Art Deco numerals, hash marks ending in squares, and various crosshairs. The name 'Paul Newman' comes from American driver and actor Paul Newman (1925-2008) whose own exotic dial Daytonas became the catalyst for the reevaluation of the once unpopular dial design.
Pawl	See 'click'.
PCG	Pointy Crown Guards. Rolex nomenclature for the pointy crown guards of the early iterations of the reference 1675 GMT-Master. Also see ‘El Cornino’.
Peacock	A nickname for the Grand Seiko reference SBGJ227 GMT and all other watches with the same radially woven texture. The name likely comes from the SBGJ227's green color and intricate texture which is reminiscent of the plumage of a peacock.
Peacock	A nickname for several Seiko models throughout history which have elaborate textured blue/green dials. The two key models dubbed ‘Peacock’ are the Seiko Superior 3883-7000 which is more commonly referred to as the ‘Morpho’ or ‘Butterfly’, and the Grand Seiko SBGJ227 Hi-Beat GMT which sports a blue-green dial with a concentrically woven texture. The nickname is now used as a name for the dial texture regardless of color.
Pearling	A method of finishing where overlapping circles are ground into metal with an engine that spins an abrasive disc or wire brush. Also known by the French terms ‘perlage’ and ‘perlée’.
Pencil Hands	A style of hands distinguished by a thin base tapering to a straight, long body which tapers to a triangular tip. A pencil hand resembles an archetypal pencil. The difference between a pencil hand and the similar baton hand with a pointed tip is that a baton hand has no taper from the base to the neck. Pencil hands may be lumed or unlumed.
Pendant Watch	A watch designed to be worn around the neck like a necklace. Pendant watches were commonly worn by women in the 19th and early 20th centuries. They later became popular targets of conversion into wristwatches due to their small size.
Pepsi	A nickname for a bi-color bezel consisting of blue and red. It is most famous as the nickname for the Rolex GMT-Masters and GMT-Master IIs starting from reference 6542 to 126710BLRO, GMT watches with blue and red bezels.
Peripheral Rotor	A type of oscillating mass in an automatic mechanical movement that is a C-shaped piece of metal that orbits the movement at its periphery. A peripheral rotor provides the convenience of a conventional automatic movement while providing an unobstructed view of the movement architecture. It also eliminates the extra height the rotor adds to the movement at the expense of a increased circumference.
Perlage	(French) Pearling. Also known as ‘perlée’.
Perpetual Calendar (QP)	In watchmaking, a perpetual calendar complication has a mechanically programmed memory of the lengths of all months in a four year cycle. This allows a timepiece with this complication to accurately display the last day of each month and progress immediately to the first of the next (e.g. it will show all 31 days for January, only 28 for February, and 30 for April). Its ability to calculate leap years allows it to add February 29th every four years. Perpetual calendars, also known by enthusiasts as a 'QP' (derived from French 'quantième perpétuel'), are considered high complications. However, most QPs do not have the ability to adjust for years that omit the leap day despite being divisible by 4 (of which there are three out of four hundred years, or a complete leap cycle). The next such year is 2100, which means most QPs will have to be manually adjusted then.
Petite Seconde	(French) Small seconds.
Petite Sonnerie	(French) 'Small strike'. A strike sequence that chimes every full hour and every quarter after the hour. In some instances an hours-only strike sequence may also be called a petite sonnerie as it is technically still lesser than a grande sonnerie. In modern times many watches are capable of switching between petite and grand sonneries.
Pheon	See 'broad arrow'.
Philippe Dufour	(1948-) A watchmaker hailing from and based in Le Sentier of the Vallée de Joux, Switzerland.
Phillips Terminal Curve	See 'terminal curve' and 'Breguet overcoil'. Named after mathematician and engineer Édouard Phillips.
Photovoltaic	The quality of converting light into electricity. Also see ‘photovoltaic cell’.
Photovoltaic Cell (PV cell)	An electronic device that converts light into electricity via the photovoltaic effect. Typically made of silicon. In watchmaking, PV cells are installed onto the dial and charge the batteries or capacitors of light-powered watches.
Piaget	A watch and jewelry manufacturer established in La Côte-aux-Fées, Switzerland in 1874 and now headquartered in Plan-les-Ouates, Switzerland. Piaget is owned by Richemont.
Pie Pan	A nickname for examples of the Omega Constellation family which feature pie pan dials.
Piece	Watch collecting parlance for any individual watch or clock.
Pièce Unique	(French) A watch or clock that is alone in its configuration with no identical examples in existence. A pièce unique is typically made on special order and may be a unique configuration of an existing reference or constructed from the ground up for the client. These pieces are generally highly desirable, especially if they were executed by reputed watchmakers or manufacturers. Also see 'unique'.
Piezoelectricity	The ability to produce an electrical charge with the application of mechanical stress. Inverse piezoelectricity is the opposite phenomenon where an electrical charge will cause the material to bend. In watchmaking, the (inverse) piezoelectric property of quartz causes the crystal to warp slightly and return to shape with the application and cessation of an electrical charge. The crystal generates a small charge of its own when returning to its original shape. This piezoelectricity allows the quartz crystal to serve as a frequency standard for the integrated circuit to count.
Pillow	A piece of watch furniture meant to have a watch strapped around it. Usually made of velvet, silk, satin, or other soft fabrics and stuffed with plushy material. Similar to a cushion.
Pilot/Aviator Watch	A category of wristwatch designed for pilots. Pilot watches come in many styles but almost universally have legible, high-contrast dials and a degree of magnetic resistance. While some of the earliest men's wristwatch designs were made for use while operating an airplane, the archetypal pilot watch as we know it today arose during the Second World War. Civilian pilot watches were developed most in the post-WWII commercial aviation boom. Pilot watches are well used by military pilots to this day, who are sometimes gifted these watches as unit memorabilia.
Pin	A metal catch in the form of a rod with a slight hook. The pin goes through an adjustment hole in the strap. Also called a 'tang' or 'ardillon'.
Pin Buckle	By far the most common type of buckle. The pin refers to the metal catch that is mounted to the buckle loop. It is also referred to as a tang or ardillon.
Pinion	A small gear. A pinion usually has anything between 6 to 14 leaves. Also see 'wheel'.
Pink Gold	An alloy used in the manufacture of watches. Abbreviated Pg. Along with rose gold and red gold, pink gold is a gold-copper alloy and generally has the lightest red color out of the three. It has the lowest copper content and highest white metal content to achieve this color, usually at about 20% copper and 5% silver.
Pink Panther	A nickname for a GMT-Master ‘Fuchsia’ which has turned exceptionally pink. See ‘Fuchsia’.
Pip	A small disc with luminous material which serves as a luminous marker in a rotating bezel.
Pivoted Detent Bridge (chronograph)	Another name for the coupling wheel bridge.
Pivoted Detent Spring (chronograph)	Another name for the coupling arm spring.
Plate	A large piece of metal that provides structure in a movement.
Plateau	(French) See ‘roller table’.
Platinum (Pt)	An element often used in the manufacture of watches. Abbreviated Pt. Platinum is naturally white, very dense, ductile, and extremely non-corrosive. Not to be confused with white gold, which is an alloy. Platinum is naturally white, whereas white gold is not. Platinum is harder and denser than white gold. It is also more ductile, meaning that white gold may chip or flake off from an impact that will merely dent platinum without losing any metal. Platinum has its own patina where scratches, dents, and bruises simply displace the material, resulting in a satin and sheeny surface. In watchmaking platinum is usually mixed with a small amount of iridium, ruthenium, and sometimes cobalt for ease of casting. As it is not gold, the purity of platinum is measured in fineness out of 1000 parts. Typically platinum will be 950Pt, which means it is 95% platinum.
Plongeur Hands	A style of hands distinguished by a thick, truncated, pencil-shaped hour hand mounted to a skinny base and a massive, truncated, sword-shaped minute hand also mounted to a skinny base. Plongeur seconds hands come in various forms but usually have a rectangular lume plot towards the tip. ‘Plongeur’ is French for ‘diver’ and thus plongeur hands are always lumed.
Plume/Feather Hands	A style of hands distinguished by a thin base tapering gently to broad shoulder which narrows to a radical and curved taper at the neck, topped off with a long and thin pointer tip. The plume hand resembles a feather with the calamus/shaft (the quill end) serves as the pointer. Plume hands are typically not lumed.
Pocket Watch	Also spelled 'pocketwatch'. A watch designed to be carried in a pocket. Pocket watches may be fastened to a belt or other article of clothing with a chain or lanyard.
Pogue	A nickname for the Seiko reference 6139-6005 automatic chronograph with a yellow sunburst dial, worn by Colonel William R. Pogue in outer space during the Skylab 4 mission from 1973 to 1974. There are disputes concerning the range of watches that can be dubbed 'Pogue'. Some consider the 6139-6002 as a legitimate Pogue as well due to its minor differences. Others consider all yellow dial 6139 series chronographs as Pogues, while some others call any watch in the entire 6139-600X family a Pogue. Regardless, the 6139-6005 is universally regarded as the 'True Pogue'.
Pointer	A component of a clock that displays information by pointing. Technically, the pointer is a type of hand and the hand is a type of pointer - they are synonymous. However, in common usage a pointer usually refers to a hand that points to information other than the time such as the day, date, or power reserve. Unlike a hand, a pointer may be stationary and simple point to a fixed position while a rotating disc adjusts its position to update information such as minutes, date, or day.
Poising	The adjustment of the weight distribution of a balance wheel. Poising can be done via adjustment of timing screws, masselottes/inertia blocks, cutting, indentation, or biased weight distribution.
Polar	A nickname for the Rolex Oyster Perpetual Explorer-II reference 16570, an Explorer-II with a white dial, white lume plots, and a red GMT hand. The name comes from how all of the dial excluding the dial printing is white. It is sometimes confused with its predecessor the reference 16550, which has been dubbed 'Panna' due to its cream patina.
Polish Mesh Bracelet	A style of mesh bracelet with a weave pattern believed to originate in Poland. Known as 'maille polonaise' in French. Polish meshes tend to have the links arranged in a herringbone-like pattern. Also see 'Milanese mesh'.
Polishing	A method of finishing where the metal surface is rubbed to a smooth finish with minimal imperfections and maximal reflections. See 'mirror polish', 'mirror finish', 'black polish', 'spéculaire', 'block polish', and 'Zaratsu' for different levels and types of polishing.
Polishing Wood	A piece of wood that is used to polish cases and movements. Polishing woods are mostly used for finer polishes such as chamfers and bevels.
Polonais	(French) Short for 'maille polonaise'. Polish mesh.
Pontife/Pontif Hands	A style of hands distinguished by an hour hand with an enormous ring towards the tip and extremely thin minute and seconds hands. Pontife hands sound similar to moon hands in concept but look very different because of the thinness of the lines and the hugeness of the ring. Pontife hands are not lumed.
Position	In watchmaking, 'position' refers to the physical orientation of the timepiece. A mechanical watch movement is affected by gravity differently depending on this orientation. This is particularly important for wristwatches as they are constantly moving around instead of staying upright in a pocket most of the time. Watchmakers measure a movement's accuracy in many positions (e.g. dial faced down, dial faced up, laid on each side, etc.) and usually make note of how many positions the watch was tested in on a plate or bridge of the movement.
Positive Display	An electronic digital display (LCD or MIP) where the assets are presented in a darker color than the background.
Potato (Seiko)	A nickname for the Seiko caliber 965 which entered the 1965 and 1966 Neuchâtel Observatory chronometer competitions. The nickname comes from the movement’s interesting shape.
Pounder	A nickname for the Audemars Piguet Royal Oak Offshore reference 25721BA. The nickname comes from the all-gold watch’s incredible weight at around 420 grams. It was also called the ‘Beauty’ to contrast with the ‘Beast’.
Power Reserve	The total amount of energy a movement can store. Usually refers to rechargeable power sources like mechanical mainsprings or electrical capacitors and not replaceable batteries. Power reserve is measured in hours or days.
Power Reserve Indicator	A complication that indicates the level of remaining energy.
Pre-moon Speedmaster	A nickname for Omega Speedmaster references released before the Apollo XI moon landing on the 20th of July 1969. This includes references 2915, 2998, 105.002, 105.003, 105.012, and 145.012. The first iterations of ref.145.022 which started production the year before the lunar mission are transitional references. These watches fall under ref.145.022-68. The pre-moon Speedmasters are diverse as they span the twelve most eventful years of the Speedmaster family’s rapid development. Nonetheless, all references but the few ref.145.022-68s are equipped with the cal.321 and feature an applied Omega logo on a stepped dial. The ref.145.022-68 (the only pre-moon 145.022 reference) was equipped with the cheaper cal.861 but some dials had applied logos. Stepped dials are standard for pre-moon ref.145.022-68 as it was before the transition to flat dials in the ref.145.022-74 released in 1974.
President Bracelet	A three-link bracelet with wide and short semicylindrical links and hidden single-fold clasp produced by Rolex. The original bracelets were made for Rolex by Gay Frères. The President bracelet is featured exclusively on the Rolex Oyster Perpetual Day-Date and thus only comes in precious metals. Due to its iconic status the bracelet has been widely mimicked and copied.
President Watch	A nickname for the Rolex Oyster Perpetual Day-Date that likely arose from its so-called President bracelet, a three-link bracelet with narrow semicylindrical links that was exclusive to the Day-Date and not found on any other Rolex models. The name may also come from the fact that many United States presidents wore Rolex watches, even though they were not necessarily Day-Dates.
Printed	A component is printed when it is printed, pressed, or otherwise inked onto the dial with an instrument other than a brush.
Professional/Scuba Diver	A subcategory of dive watch that is designed for scuba diving. This subcategory is the largest and most difficult to define out of the dive watch family, and the name is not universally accepted. In the modern sense, it refers to a watch that exceeds the minimum requirements to be certified as a dive watch and can serve as the primary dive timer in a scuba dive. Generally these watches have a minimum water resistance of 200m, lumed diver indices, a unidirectional rotating timing bezel. They are typically heavier-duty than skindivers but not as thick, heavy, or water resistant as deep divers. They may be equipped with the necessary hardware for saturation diving.
Proprietary Movement	A movement that is either developed or produced internally by the watch manufacturer. Proprietary movements are similar to in-house movements but lack either in-house design or production. However, they are still proprietary to the manufacturer and thus are differentiated from 'borrowed' movements like ébauches and third party movements. A proprietary movement may be developed by someone else but purchased by the watch manufacturer or developed in-house and manufactured by a contracted facility. See 'in-house movement' for a similar term and 'ébauche' and 'third party movement' for comparison.
Protection Film	A thin and transparent film that is adhered to the surfaces of a watch to protect it from dings, scratches, and bruises. This is especially true for cases made of soft metals such as gold and for components that are susceptible to scratches such as the bracelet and bezel. Protection film can protect the resell value of a watch and might be useful if the watch is bought as an investment. Protection film is still a somewhat divisive topic in the watch community.
Pulsometer	A scale that measures heart rate. The pulsometer uses the basic formula of a tachymeter which measures frequency over a second-defined period. Because its purpose is more specific, the pulsometer specifies how many pulsations it is graduated for. If it says fifteen, the wearer will count fifteen beats of the heart immediately after starting the chronograph. The number the seconds hand indicates at the end of the fifteenth pulse is the resting heart rate. Pulsometers are frequently found in medical watches. They must be accompanied by some sort of chronograph that allows the wearer to start, stop, and reset the seconds hand at will.
Push Button Clasp	A clasp that uses a button-activated spring-loaded release and a knob to lock. Unlike the friction clasp, the push button clasp requires the wearer to depress a button or two to release the lock. It is generally slightly bulkier and sometimes less reliable due its having more moving parts, but it provides better protection against the clasp getting yanked or snagged open.
Push-piece	See 'pusher'.
Push-pull Crown	A crown that is not fastened. Most crowns are push-pull crowns. Push-pull crowns may offer some basic water resistance with gaskets but are prone to leaking when submerged deep in water. However, they are hassle-free to use and are sufficient for most watches.
Pusher	A mechanical actuator protruding out of the case which is actuated by being pushed. Also called a push-piece or button. It is perhaps the most common type of mechanical actuator and can be mounted to almost any complication including calendars (for adjustment), chronographs, worldtimers, and repeaters.
Pussy Galore	A nickname for the Rolex Oyster Perpetual GMT-Master reference 6542. The name comes from the watch's appearance on Honor Blackman's wrist when she played the character Pussy Galore in the 1964 James Bond film Goldfinger.
Qaboos Dial	A nickname for watch dials bearing the signature of the former Sultan of Oman Qaboos bin Said Al Said (r. 1970-2020). The signature is typically in red and reads ‘Qaboos’ in Arabic. Much like the more famous Khanjar-emblazoned dials, these watches were gifts from the Sultan and his government. Unlike the Khanjars, the Qaboos signature was always printed on the dial and not engraved on the caseback. The Qaboos dial and the various iterations of the Khanjar dial are collectively called the ‘Oman dials’.
Quarter Rack	A rack which interacts with the quarter snail and the hammer trips of the bass and treble hammers. The quarter rack has two sets of four teeth as it must interact with two different hammer trips.
Quarter Repeater	A striking complication that repeats (chimes) the hours and quarters on demand. Typically the hours are sounded with a bass note and the quarter with a treble note or one of each.
Quarter Snail	A snail cam which transmits information on the current quarters to the quarter feeler so that a repeater can announce the current quarters. The quarter snail is in the shape of a logarithmic spiral with four steps.
Quartz	A crystalline mineral composed of silicon dioxide. It is the second most common mineral in Earth's crust but can also be artificially farmed. In watchmaking quartz is important as a component for quartz crystal oscillators which make sure quartz clocks keep good time.
Quartz Crystal	See 'quartz'.
Quartz Movement	A movement which uses a quartz crystal as a timing reference and an electric power source such as a capacitor or battery. While technically a type of electronic movement, the quartz movement is virtually alone in this category and is thus an interchangeable term.
Quartz Oscillator	See 'crystal oscillator'.
Quartz Watch	A watch that uses a quartz movement. Also see 'quartz movement'.
Quebec Timezone	Military timezone name for UTC+4.
Quick Adjustment	A feature of certain clasps that allows the wearer to quickly expand the clasp according to their needs. Most clasps with quick adjustment offer an immediate 5mm or more extension with a hidden folded link tucked into the clasp, sliding anchor point, or a ratcheting extension. Quick adjustment is useful for expanding the bracelet during hot and humid days when the wrist expands, or for wearing the watch over the cuff when diving. Quick adjustment makes up for the lack of adjustability in clasps compared to buckles. Also see 'microadjustment'.
Quick Change Spring Bar	A spring bar with a protruding knob that can be pulled back with a fingernail, eliminating the need for a tool.
Quraysh/Quraish	(Arabic) The Hawk of Quraish. Also spelled 'Quraysh'. The Quraish were the Arab clans that inhabited current-day Mecca in pre-Islamic Hejaz. The falcon or hawk is claimed to be their symbol. The Quraishi Hawk is a common device in Arab heraldry and serves as the national emblem of several countries. In watchmaking, the most common Quraishi Hawk emblazoned on dials is that of the national emblem of the United Arab Emirates. Watches with these markings are associated with the UAE Ministry of Defense.
R Stone	A rare term for the entry pallet of the pallet fork. Presumably short for ‘right stone’ as the entry pallet is on the right arm of the pallet fork from the balance’s point of view. Also called the ‘receiving stone’.
Racing Strap	A style of strap, usually leather, that is perforated with large holes. Also known as a 'rally strap'. The holes may be a stylistic choice or help with breathability.
Racing Watch	A category of wristwatch designed for racing drivers who needed a chronograph and tachymeter to determine their average speeds. While obsolete in modern motorsports, racing watches are important vestiges of racing culture and history. They are still widely worn by drivers and fans, and are appreciated outside the sport for their unique and colorful aesthetics.
Rack	A component in a repeater which samples the current time from the snail cams and relays the information to the hammer trips to activate the hammers. One end of the rack is a feeler which interacts with the snail cam and the other is lined with teeth which interact with the hammer trip. The rack also has a set of teeth on its side/lengthwise which is meant for the driving hook to grab onto so that it can be pulled along the hammer trip. Many racks somewhat resemble carabiners and are skeletonized for weight reduction and to free up more space in the movement.
Rack-and-pinion	A gear combination consisting of a spur gear (pinion) and a gear rack (rack). It converts rotational motion to linear motion. Rack-and-pinion combinations are rarely seen in watchmaking.
Radial Dial (Rolex)	In Rolex nomenclature, a radial dial can be one of three dial configurations. The first is on certain examples of the GMT-Master ref.1675 and features smaller hour markers that are moved closer inward and away from the minute track. This dial is also called a ‘mini dial’ due to its smaller lume plots. The second is on certain ref.1500 Datejusts and features extra long minute hashes. There is also a variation called the ‘half-radial dial’ where every other minute hash is long. The third is on certain 11623X series Datejusts and features radial numerals and/or some radial pattern such as concentric circles or radial fluting.
Radial Numerals	Numerals whose bases always face the center of the dial as opposed to conventional numerals which are flipped for better legibility from four o’clock to eight o’clock.
Radial Striping	A type of striping where the stripes radiate from a central point instead of being arranged in straight parallel lines. Also see 'striping'.
Radium	A radioactive element used for lume. Abbreviated as Ra. Radium was used as lume as late as the 1960s until it was replaced with safer and longer lasting alternatives. While its self-luminescence and brightness were advantages, it posed a risk to those directly exposed to it in the manufacturing process due to its intense radiation.
Radium Burn	A phenomenon where radioactive lume causes nearby surfaces to appear a scorched orange and/or black. This usually affects the hands, dial, and crystal. Radium burn is usually the result of decades of radiation and will usually occur only when the radioactive material is constantly in one spot. Thus, most radium burns are caused by stationary markers. Radium burns caused by hands are the result of the watch sitting still in a drawer or safe for many years, which is why many collectors see it as a potential marker of good condition and light wear. Like patina, radium burn cannot really be controlled and may give charm and character to the dial or render it completely disfigured. Nonetheless it is at the very least a solid marker of authenticity.
RAF Strap	A style of one-piece strap that is constructed using one piece and a fabric keeper. The RAF strap was one of the first one-piece fabric straps and one of the precursors to the now ubiquitous one-piece fabric straps. It was adopted by the Royal Air Force in the post-WWII era, hence the name. Also see 'nato strap', 'zulu strap', 'Pearson strap', and 'A.F.0210 strap'.
Rail Dial (Rolex)	In Rolex nomenclature, a rail dial is a dial where the Cs of ‘Chronometer’ in ‘Superlative Chronometer’ and ‘Certified’ of ‘Officially Certified’ line up. This can be found on Sea-Dweller ref.1655 and Explorer-II ref.1665 and ref.16650.
Railroad Chronometer	An extremely accurate timepiece - usually a pocket watch but sometimes a wristwatch - meant to keep time for personnel operating a rail system. While these watches are most associated with conductors, engineers and switch operators also needed synchronized railroad chronometers to coordinate the movement of trains and switch rails. These watches became necessary in the 19th century as uniform time standards and high accuracy timepieces decreased the number of rail accidents. As such the watches were usually inspected for adequacy under a certain standard that dictated dial designs to improve legibility, movement components to improve accuracy, and other performance standards for anti-shock, anti-vibration, and anti-magnetism. While these watches are no longer required today, some rail operators still issue railroad chronometers. It is also a fairly popular style of wristwatch due to its simple and legible design.
Railroad Track	A track that resembles a railroad. Typically it describes an enclosed track consisting of two concentric circles and hash marks running between them.
Railroad Watch	A category of wristwatch based on the railroad chronometer. The majority of real railroad chronometers were pocket watches, even after the widespread adoption of the wristwatch. Most railroad watches are simply inspired by the unique aesthetic of the original railroad chronometers. Nonetheless, they still come fitted with highly legible regulation dials and anti-magnetic features.
Rainbow	A nickname for a watch embellished with colorful gemstones.
Raised	A component is raised when it protrudes above the dial surface. It is used mostly interchangeably with 'applied', although the latter term refers to components that have been finished separately and then attached to the dial whereas raising is a broader technique.
Ratchet	A mechanical device that allows motion in only one direction. Typically it is composed of a ratchet wheel and click. A ratchet wheel is a circular toothed wheel which engages with the click or pawl which interacts with the teeth to allow motion in the direction of the slope but prevent it in the direction of the face. Ratchets are utilized in many applications which should only turn in one direction such as barrels.
Ratchet Wheel	A wheel that interacts with a click to rotate in only one direction but not the other. Together they make up a ratchet mechanism. A ratchet wheel typically has asymmetrical saw-teeth but may have symmetrical teeth with certain click designs.
Rate	The amount of time a timepiece deviates over a certain period of time. Unless otherwise specified, rate refers to a timepiece’s daily rate. Particularly accurate timepieces may post monthly or yearly rates. Rate is measured in seconds, and uses a plus (+) symbol to indicate time gained and a minus (-) symbol for time lost. For example, a watch whose rate is +1 is a watch that, over 24 hours, will over-indicate the time by one second.
Rattrapante	(French) To catch up. Synonymous with ‘split-seconds chronograph’.
RBOW	Rainbow. Rolex nomenclature for a bezel set with multi-color gemstones.
RBR	Ronde, Brillants. Rolex nomenclature for a bezel set with round cut diamonds.
RCO Daytona	See ‘Oyster Sotto’.
Recoil Anchor Escapement	See 'anchor escapement'.
Recoil Click	A ratchet-and-click mechanism that slightly unwinds the mainspring when it becomes too close to being fully wound. The name comes from how the click allows the barrel to recoil backwards. The recoil click is effectively the successor to the stopwork as it performs the same function of preventing the mainspring from exerting excessive torque. While the recoil click alone is less effective than the stopwork, it is much simpler and effective enough due to the much longer length of modern mainsprings. Modern mainsprings have a much longer optimum operating range and only require a small amount of unwinding to avoid the high torque area. Hence, the simpler recoil click is more suited to modern mainsprings as stopworks tend to excessively limit the barrel’s activity.
Rectangular Case	A case shape distinguished by a rectangular profile. Sometimes called a tank. See ‘tank’.
Red Alpinist	A nickname for the Seiko Alpinist SCVF00X series expedition watches with the 'Alpinist' wordmark in red text. It may also include the subsequent generation of Alpinists sporting the 8F56 quartz movement, namely the SBCJ0XX series which also had the red wordmark with the exception of the SBCJ023 special edition for the Seven Summits Actions for Sustainable Society (SSASS).
Red Gold	An alloy used in the manufacture of watches. Abbreviated Rg, which can be confusing with the very similar rose gold. Along with rose gold and pink gold, red gold is a gold-copper alloy and generally has the strongest red color out of the three. This is achieved with about 25% copper content in 18K red gold. It is also the least commonly seen of the three in watchmaking.
Red Sub	A nickname for the Rolex Oyster Perpetual Submariner reference 1680, which features a line of red dial text. The 'Submariner' text was in red for only the first generation of the ref.1680 from 1967 to 1975, after which it was replaced with white.
Redflake	A nickname for the Grand Seiko reference SBGA211G, an SBGA211 made for the AJHH (Association Japon de la Haute Horlogerie/Japanese Association of High Horology). The watch is an SBGA211 'Snowflake' with red accents on the dial-side and a red exhibition caseback, hence the name 'Redflake'.
Redial	The refinishing of a dial. While a holistic term, it especially refers to the correction of faded or erased dial text and markings.
Reduction Gear/Drive	A device that changes the transferred rotational speed of a wheel. A reduction drive in a movement typically works by meshing a pinion (small gear) with a wheel (large gear) so that many rotations of the pinion equal a single rotation of the wheel. It is most frequently used for indicating the hours. Also see ‘motion work’.
Reed's Regulator	See 'swan neck regulator'.
Reference	A single clock with a unique reference or a group of watches that share a reference number (e.g. 3970G, 3970J, etc.). In common use, 'reference' refers to a certain model of watch as they can be collectively referred to by their shared reference number. Similar to 'piece', but whereas 'piece' always denotes a single, individual watch, 'reference' denotes all the watches that share the reference number even if there is only one. Ex) "This is a unique reference produced for a very special client of the company." Also see 'reference number'.
Reference Number (ref.)	More commonly referred to simply as 'reference' or 'ref.'. A reference number is a unique alphanumerical designation given to a model of timepiece. Reference numbers are decided internally by the manufacturer and may overlap with those of other manufacturers. The amount of information represented in the reference number and thus how specifically it describes the watch varies. For example, the Patek Philippe 3940 is a family of perpetual calendar wristwatches. 3940G denotes white gold, 3940J yellow gold, 3940P platinum, and 3940R rose gold. Depending on the scope of the conversation it can be said that all four 3940s still share a reference number, because they are simply different case material variations of the same model. Watch enthusiasts commonly refer to watches by their reference numbers in lieu of nicknames for convenience, accuracy, and/or pedantry. Therefore, 'reference' is interchangeable with 'model'. Not be confused with 'serial number'. Also see 'reference'.
Regatta Watch	A category of wristwatch designed for boat races. A regatta/boat race starts in a unique way due to the fact that watercraft cannot be lined up at a start line. Boats may start speeding towards the invisible start line well before the start of the race as long as they do not cross it before the starting gun. This makes pre-start maneuvers important as the boat should cross the start line at maximum speed in the most advantageous position at the moment the starting gun is fired. Regatta watches utilize countdown timers that count down from 10 (sometimes 5 or 15) minutes, which are started with the firing of the 10 minute gun. They are recognized for their quirky and colorful countdown timers.
Regulate	To adjust the balance of the movement in order to achieve better accuracy.
Regulator (component)	A component that assists in regulating the movement by adjusting the free length of the balance spring. The regulator is mounted on a balance cock/bridge and can come in several forms. These include the Bosley regulator, snail cam regulator, and swan neck regulator. Not all movements have regulators. Balances without regulators are called 'free-sprung balances'.
Regulator (style)	A type of dial configuration where the hour, minute, and seconds hands are separated instead of being mounted on the same handstack and rotating concentrically. The term 'regulator' comes from regulator clocks which would serve as time references for setting the time on timepieces - the separated hands were originally for legibility. Today the regulator layout is a stylistic choice.
Rehaut	(French) French for flange. In watchmaking, the rehaut is the wall that surrounds the dial and serves as the spacer between the dial and crystal where the handset can sit. While most watches have some form of rehaut, some watches with domed crystals do not have rehauts as the dome creates enough space for the handset.
Reissue	A watch that is a later recreation of a previous reference, usually with a high degree of faithfulness to the original. Reissues are usually labeled as such and thus can only be released by a company with the rights to the original design. They possess the technology and details of their time while adhering to the design principles of the original reference.
Relume	The replenishment and reapplication of fresh lume to a watch's dial and/or hands.
Remontoir d’Égalité	(French) See ‘constant force mechanism’.
Remontoire	(French) ‘Winder’. A secondary power source which powers the timekeeping organ and replenishes its energy from the primary power source. A remontoire runs the timekeeping organ from up close instead of relying on a long going train which is prone to inefficient and incomplete power delivery. While the power loss is negligible for most pedestrian timepieces, the remontoire is useful for high precision timepieces. The remontoire also overcomes the problem posed by Hooke’s law by constantly winding and unwinding, resulting in a very constant average torque figure as opposed to the constantly declining torque of the mainspring. Due to its function of providing constant force to the balance, the remontoire is a type of constant force mechanism.
Repeater	A complication, or a watch with such complication, which repeats on command. A complication that only chimes 'in passing' is not a repeater. A repeater possesses both a mechanical memory to remember how many strikes of which kind are due for each minute of a 12-hour cycle, and a mechanical feedback system which relays the current time to the cadrature so it may refer to aforementioned memory when activating its hammers.
Repetition	In watchmaking, 'repetition' refers to the announcement of time via sound on command. A watch that is capable of repetition is called a 'repeater'.
Replica	A euphemism for a fake/counterfeit clock, usually a watch.
Reset	In watchmaking, 'reset' refers to the returning of a function to its default position. This usually refers to hands, especially chronograph hands which can be reset to zero after being used. Also see 'zero reset seconds'.
Reset Cam	A chronograph mechanism that is connected to the chronograph hands and executes their reset upon the activation of the reset pusher. As the cam is shaped like a human heart, it is also called a ‘heart piece’. The reset cam is the reason mechanical chronographs reset in an instant unlike most quartz chronographs.
Reset Lever	A component of a chronograph mechanism which, when activated by pushing the reset pusher, moves to slam the heart-shaped reset cam(s) back to zero with the hammer.
Reset Pusher	A pusher on a chronograph that resets the hands of the chronograph back to zero.
Resonance	The phenomenon that occurs in an object or system when it is exposed to vibrations that match its frequency. In watchmaking, resonance specifically refers to the phenomenon of two separate but nearby oscillators eventually synchronizing frequencies after a period of time. At first a contentious subject, several horologists posited that two balance wheels oscillating next to each other would not only run at a more stable rate due to this synchronization, but also increase the accuracy of the timepiece.
Retailer Signature	A print, engraving, or some other mark that indicates the retailer of a timepiece. This practice, virtually nonexistent today, was relatively common for respected jewelers and retailers until the 1970s. When a retailer signature is stamped onto the dial along with the manufacturer's signature, the dial is 'double-signed'. Retailer signatures may also appear on the caseback. Watches bearing a retailer signature are highly collectible and may command large premiums, especially depending on the reputation of the retailer.
Retard	(French) Delay. Commonly written in full or abbreviated as 'R' on balance cocks for adjusting the regulator. Pointing the index towards A slows down the watch.
Retour en Vol	(French) ‘Return on flight’. Flyback.
Retro Racer	A nickname for the Seiko references 6139-8020 and 6139-8029, distinguished by a lug-less design, holed bracelet, and colorful dials. The name likely comes from its distinctly 1970s look.
Retrograde	A mechanism and display style where the hand does not make a full rotation but rather sweeps a fan-shaped circular arc, retracing back to its original position upon reaching the end of the arc. Retrograde displays are most commonly used for pointer dates and power reserve indicators. Occasionally watches employ retrograde display for the time as well.
Reverse Lollipop Hand	A hand style that consists of a circular counterweight. Almost exclusively used for seconds hands.
Reverse Panda	A black dial with white sub-registers.
Ripley	A nickname for the Seiko reference 7A28-7000 and its reissue, SCED035 which was worn by Sigourney Weaver as Lieutenant Ellen Ripley in the 1979 film Alien. The watch is also called 'Giugiaro' after its designer.
Rising Sun	A nickname for the Omega Speedmaster Professional reference 522.30.42.30.06.001 limited edition for the 2020 Tokyo Olympics. The name ‘rising sun’ comes from the red bezel and a popular trope in Japanese culture.
Rivet	A fastener consisting a shaft and two heads. In watchmaking, rivets are used to hold together links of a bracelet. However, they are no longer commonly used as spring bars and screw bars have replaced the more finicky rivets. Rivets for bracelets are not true rivets in the sense that the separate head is screwed on instead of being cut and deformed like a shop head. Also see 'rivet bracelet'.
Rivet Bracelet	A bracelet with links connected by rivets. Rivet bracelets can be distinguished by round rivet heads on the sides of the links. While rivet bracelets have fallen out of popularity in favor of less complicated and more secure fasteners, the style is often recreated.
ROC Daytona	A nickname for Rolex Oyster Cosmograph Daytonas with the Oyster Signature above the Cosmograph signature. This configuration was more common than the so-called RCO configuration which is now extremely valuable and rare. See ‘RCO Daytona’ and ‘Oyster Sotto’.
Rolex	A watch manufacturer established in London, England in 1905 and now headquartered in Geneva, Switzerland. Rolex is owned by the Hans Wilsdorf Foundation.
Roller	A component of the escapement that is attached to the balance and swings with the balance wheel. The roller serves as the intermediary between the balance and escapement through a small protruding jewel called the ‘impulse jewel’. A movement may have more than one roller. Also see ‘impulse roller’, ‘roller table’, ‘safety roller’, ‘single roller escapement’, and ‘double roller escapement’.
Roller Jewel	See ‘impulse jewel’.
Roller Pin	See ‘impulse jewel’.
Roller Table	An alternative name for the roller, especially the impulse roller in a double roller escapement. So called due to its wide surface. Also known as ‘plateau’, particularly in French.
Rollie	A colloquial nickname for a Rolex wristwatch.
Rolling	A metalworking technique that involves the shaping of a flat metal workpiece by pressing it against a cylindrical workpiece, bending it into an arc. In machining terms, this method is technically called ‘curling’ and is a type of stamping/pressing. ‘Rolling’ would mean something else, such as the rolling used to change the properties of metal or roll bending. However, in watchmaking, the term is used primarily to describe rolled links and a distinction is made between rolling and stamping especially when describing the manufacturing techniques of bracelet links.
Roman Numerals	A type of numerals commonly featured on watch dials. The roman numeral system uses the Latin alphabet and designates a fixed number value to the letters I, V, X, L, C, D, and M.
Romeo Timezone	Military timezone name for UTC+5.
Root Beer	A nickname for the Rolex Oyster Perpetual GMT-Master II references 1675/3, 16753, 16713, 126711CHNR, and 126715CHNR. These five watches are all variations of the GMT-Master II with tones of brown and gold. The nickname comes from the brownish color tones that the watches share. 1675/3, 16753, and 16713 are similar in color as they have brown dials and brown and gold aluminum bezels. The 126711 and 126715 have Cerachrom bezels that are somewhat similar to the original Root Beers as they have brown, black, and gold bezels.
Rose Engine Lathe	Also simply called 'rose engine'. A type of geometric lathe that is capable of producing intricate patterns that resemble flowers, hence the name. Unlike many lathes which simply turn, the headstock on a rose engine pumps back and forth on the spindle axis. Rose engines are appreciated not only for the beautiful patterns they produce but also for their own beauty.
Rose Gold	An alloy used in the manufacture of watches. Abbreviated Rg, which can be confusing with the very similar red gold. However, rose gold is used far more commonly in watchmaking. Along with red gold and pink gold, rose gold is a gold-copper alloy and is generally in between the other two in redness. It has lower copper content than red gold and lower white metal content than pink gold to achieve this color.
Rotating Bezel	A bezel which rotates to perform a function. Rotating bezels are usually textured at the rim for better grip.
Rotating Internal Bezel	A rotating bezel that is contained inside the watch crystal. Technically, an internal bezel is not a real bezel but a rotating rehaut. It is called a bezel because it is similar in function and appearance to a rotating bezel. The action of the inner bezel is controlled by either an actual rotating bezel or a crown. The latter is usually done with a proprietary crown whose sole job is to control the inner bezel. Rotating internal bezels can be practical because there is a lower chance it will be knocked into a different position and because it lowers the profile of the watch. However they are less accessible and usually chosen for aesthetic purposes. Compressor-style watches often feature inner bezels.
Rotor	A moving component. In watchmaking it mostly refers to the rotor-weight, which is a form of oscillating mass. See 'oscillating mass'.
Rotor Wobble	The obviously noticeable wobbling of the oscillating mass on a wristwatch with an automatic movement, especially in daily wear. While all automatic movements will have noticeable rotor movement when shaken violently enough, rotor wobble refers to when it is noticeable even with the slightest of wrist motions. Rotor wobble may be more pronounced on older or affordable movements and is sometimes seen as a sign of poor quality, though this is not always true.
Rotor-weight	See 'oscillating mass'.
Roue à Colonnes	(French) Column wheel.
Roulette	In watch collecting parlance, ‘roulette’ can mean ‘roulette numerals’, a ‘roulette dial’, or ‘roulette date wheel’. All are named after the alternating colors and/or the composition of a roulette wheel.
Roulette Date Wheel	A date wheel with alternating colors, usually black and red.
Roulette Dial	A dial with roulette numerals. By default, most roulette dials are also sector dials as the dial is divided into annular sectors.
Roulette Numerals	Roulette numerals are radial numerals contained within an annular sector. Radial numerals are numerals whose bases always face the center of the dial as opposed to conventional numerals which are flipped for better legibility from four o’clock to eight o’clock. An annular sector is a divided sector between two concentric circles. While roulette numerals are often featured on the dial, some rare instances feature them on the bezel. Roulette numerals do not have to have alternating colors.
Round Case	A case that is round. Antonymous with 'shaped case'.
Rounded Square Case	A case shape distinguished by a square profile with rounded edges and/or concave sides. More commonly known as ‘carré galbée’ in certain brands.
Royal Broke	A nickname for the Casio G-SHOCK 2100 series watches. It is a tongue-in-cheek name that pokes fun at the watches' resemblance to the Audemars Piguet Royal Oak, which is more than a hundred times more expensive at retail. Also see 'Casioak'.
Rubber Strap	A strap that is made of rubber, silicone, or other rubbery materials. Usually composed of two pieces.
RUBI	Rubis. Rolex nomenclature for a bezel set with baguette cut rubies.
Rubidium (Rb)	An element that is sometimes used as the frequency reference in atomic clocks. Rubidium clocks generally follow the same principle as cesium clocks.
Rubis	(French) Jewel.
SA	Saphirs. Rolex nomenclature for a bezel set with sapphires.
SABLV	Saphirs Bleu Vert. Rolex nomenclature for a watch set with blue and green sapphires.
SABR	Saphirs, Brillants. Rolex nomenclature for a watch set with sapphires and diamonds
SACO	Sapphire, Cognac. Rolex nomenclature for a bezel set with cognac-colored sapphires.
Safety Roller	An extra roller added to the main roller table in a double roller escapement to decrease the diameter of the roller engaging with the guard dart.
SAFU	Saphirs Fuchsia. Rolex nomenclature for a bezel set with baguette cut fuchsia sapphires.
SAFUBL	Saphirs Fuchsia Bleu. Rolex nomenclature for a watch set with fuchsia and blue sapphires.
SAJOR	Saphirs Jaune Orange. Rolex nomenclature for a watch set with yellow and orange sapphires.
Sallaz	(German) A now-defunct Swiss manufacturer of machinery, tools, and industrial equipment. Gebrüder Sallaz (Gebr.Sallaz) manufactured polishing machines which were exported to Japan and formed the bedrock of the now-famous Japanese polishing craft. Today the technique is branded as 'Zaratsu' by Seiko and 'Sallaz' by several other companies.
Salmon	A sort of golden, lightly orangey pink color. Used to describe dials. The color can be achieved through pink gold, rose gold, copper, or lacquer.
Samurai	(Japanese) A nickname for the Seiko SBDA001 diver and the various divers that take after it. The name allegedly comes from how the hands resemble a katana. As there is absolutely no resemblance to a katana, the nickname was likely a random Japanese word that Western collectors were aware of and justified later.
Sandblast/sand-blast	A type of abrasive blasting that blasts sand on a surface. The resulting finish is grainy and matte. It is often employed for finishing cases for tool watches.
Sandwich Dial	A dial that is composed of two or more stacked layers, usually for some kind of visual effect such as added depth or complexity. Sandwich dials typically have cutouts on the dial to expose the underlying layer which is often of a contrasting color or made of a solid block of luminous material.
SANR	Saphirs Noirs. Rolex nomeclature for a bezel set with black sapphires and diamonds.
SAPH	Saphirs. Rolex nomenclature for a bezel set with baguette cut sapphires.
Sapphire	An oxide mineral and variety of corundum, consisting of aluminum oxide. Sapphire is most famous as a blue gemstone, but there are many varieties in color and composition. In watchmaking the most common sapphire is synthetic sapphire. See 'sapphire crystal'.
Sapphire Crystal	A synthetic variant of sapphire made by crystalizing aluminum oxide at very high temperature. Also called 'sapphire glass', though it is technically not a glass. Sapphire crystal is transparent, colorless, and extraordinary hard, rating a 9 on the Mohs hardness scale. It is virtually scratch-proof and void of visible impurities, making it ideal for watch crystals. In rare occasions sapphire is used to construct completely transparent cases.
Sapphire Glass	See 'sapphire crystal'.
SARU	Saphirs, Rubis. Rolex nomenclature for a bezel set with sapphires and rubies.
Saturation/Gas Diver	A subcategory of dive watch that is designed for saturation diving. Saturation divers deal with the issue of pressurized helium infiltration, which may cause the watch crystal to blow off upon surfacing without pressure equalization. This is a common concern as helium is a key ingredient in mixed/blended gas diving because of its ability to prevent narcosis. As helium atoms are tiny, they can enter a watertight watch case with ease. Watches may address this issue with a helium escape valve (HEV) or a monobloc case. Technically a saturation diver may be rated to any depth as a watch's ability to withstand mixed gas diving is irrelevant to its water resistance rating. However they are typically accompanied with high levels of water resistance due to the typical depths of saturation diving as well as marketing.
Savonnette (movement style)	A style of movement where the subseconds subdial is mounted perpendicularly to the crown stem, putting the crown at the three o'clock position and the seconds at six. These movements were commonly mounted in savonnette pocket watches, hence the name. This configuration is now standard in wristwatches as many wristwatches have their crown at three and subseconds at six. Antonymous with ‘Lépine (movement style)’, even though savonnette movements still employ Lépine caliber architecture.
Savonnette (watch)	(French) Bar of soap. A style of pocket watch popular in the late 19th and early 20th centuries. It is a pocket watch equipped with a so-called savonette movement, and features a hinged front cover which protects the crystal when not in use. The name comes from the apparent likeness of the watch to a sleek bar of soap. In America savonnette watches were called 'hunter watches'. Thus, the terms 'hunter' and 'savonnette' are interchangeable in some contexts. See 'hunter watch' for a related term and 'open face' and ‘Lépine watch’ for antonymous terms. Also see ‘savonette (movement style)’.
Saw-tooth Gear	A gear with asymmetrically-profiled teeth which slope in one direction in a way that resembles a saw blade. Saw-tooth gears are useful when a wheel should only turn in a single direction. Therefore, they are common in watchmaking and can be found as escape wheels in anchor and deadbeat escapements and as ratchet wheels in any mechanism that requires interaction with a click, detent, or pawl.
Scale	Graduations on a timepiece that represent a range of values to aid a specific kind of measurement. It is similar and sometimes interchangeable with 'track'. However, whereas a track usually refers to even and linear graduations to measure such things as time or elapsed time, a scale is usually logarithmic and nonlinear. Scales usually utilize the seconds hand because it moves in the smallest increments. Thus most scales require a chronograph of some sort that allows the wearer to start, stop, and reset the seconds hand at will. Some scales are mounted on a rotating bezel to accommodate for a regular seconds hand so that the wearer can set the scale to wherever the seconds hand is.
School Watch	A watch made by a student watchmaker in watchmaking school, usually as a final project. School watches are often precious objects that set the base for the watchmaker's career going forward. Some watchmakers reference or recreate their school watches further down their careers. Also known by its French name 'montre-école'.
Scientific Dial	A vaguely defined dial style that most closely resembles a sector dial. A scientific dial is a type of sector dial and the two terms are sometimes used interchangeably. It is likely that the term is simply another name some brands called their sector dials.
SCOC Caliber	A Rolex caliber that is officially certified by a third-party testing organization to be an exceptionally accurate movement, or a ‘superlative’ chronometer. They are called SCOC calibers because they are accompanied with the dial text ‘Superlative Chronometer Officially Certified’. The first SCOC calibers, the 15XX series movements, utilized a free-sprung balance which eliminated the regulator. They used Microstella screws instead. The SCOC designation continues to this day, maintaining a free-sprung balance albeit with Microstella nuts instead.
Scratch Remover	An abrasive paste that is applied to acrylic crystals to buff out scratches.
Screw Bar	A type of bar that is fastened on both ends by screws. Screw bars are difficult to fasten and remove but are more secure than spring bars. Though somewhat rare, they can be found on some watches for stylistic or practical purposes.
Screw-down/Threaded Caseback	A type of caseback that is fastened by interlocking threads on the caseback and caseback opening. The screw-down caseback is famous for its resistance against the elements as the combination of a gasket and the interlocked threading makes it difficult for water to enter the case. Screw-down casebacks can be identified by notches, grooves, teeth, and other contact points for a caseback opening tool to grip. They also must lack visible screw heads as screws defeat the very purpose of having a screw-down caseback.
Screw-down/Threaded Crown	A crown that is fastened by threading. The inner wall of the crown is lined with threads that interlock with a threaded collar surrounding the crown stem. A screw-down crown guarantees superior water resistance than a push-pull crown.
Screw-in Caseback	A type of caseback that is fastened by screws. Screw-in casebacks use small screws to hold the caseback in place. While they may offer higher water resistance than snap backs, screw-in casebacks are still not ideal for keeping out water. Nonetheless, they are sufficient for most activities and are commonly found a wide range of watches.
Screwed Balance	A balance wheel that is adjusted with removable screwed-in weights called 'timing screws'.
Sea Urchin	A nickname for the Seiko 5 SNZF series divers. The nickname's origin is unclear, but is likely from the pronounced graduations on the rehaut and bezel that resemble the spines on a sea urchin.
Second Wheel	A component of the going train that is the second wheel to transfer energy from the unwinding of the mainspring. A coaxial pinion meshes with the first wheel and fully turns the second wheel once every hour. Therefore it mounts the cannon pinion which in turn mounts the minute hand. In many conventional movement configurations, the second wheel occupies the center of the movement. In these cases it is called the ‘center wheel’. However, the center wheel is not always the second wheel. Also see ‘center wheel’.
Seconde Foudroyante	(French) See ‘foudroyante seconds’.
Seconds Hand	The hand that points to the seconds. Makes a full rotation every minute.
Seconds Wheel Tension Spring/Pawl	A component of a chronograph mechanism that applies constant pressure to the chronograph runner/chronograph seconds wheel so that the chronograph seconds hand advances in the desired manner and so that bumps and knocks do not throw off the position of the chronograph seconds hand.
Sector Dial	A dial style that utilizes concentric circles to divide the dial space. In most sector dials, each dial element (e.g. hour markers, minute track, etc.) is allocated its own ring demarcated by concentric circles. In some instances, the crosshair dial is regarded as a type of sector dial. In the strictest sense, a crosshair dial is divided into quadrants while a sector dial is divided into rings. However, the two are not mutually exclusive and are often combined. Also see 'scientific dial'.
Secular Perpetual Calendar	A calendar complication which is an advanced perpetual calendar capable of automatically adjusting for a quirk in the Gregorian calendar where only centurial years divisible by 400 are leap years. The rule for a leap year is that every year divisible by 4 is a leap year unless it is centurial (and thus divisible by 100). However, a centurial year is a leap year when it is divisible by 400. The year 2100 CE is the next such year. A normal perpetual calendar would calculate 2100 as a leap year when it is not. A secular perpetual calendar would know to proceed to the 1st of March after the 28th of February.
Seiko	A watch manufacturer established in Tokyo, Japan in 1881. Seiko is owned by the Seiko Group.
Seikopath	A humorous and usually self-deprecating term for an enthusiast of Seiko watches. It is a portmanteau of ‘Seiko’ and ‘psychopath’ which works especially well because Seiko and psycho sound somewhat similar.
Self-compensating Balance Wheel	See 'bimetallic balance wheel'.
Self-starting Escapement	An escapement which is able to provide the initial impulse to the balance upon replenishing energy. An escapement that is incapable of self-starting must be assisted with a shake to get the balance wheel swinging, which will unlock the escape wheel and allow the power of the mainspring to take over. An escapement that self-starts will deliver the power from the mainspring and wheel train on its own as it is able to knock the balance wheel into action. Escapements that can do this include the lever and co-axial escapements.
Self-winding Movement	A movement which can be wound with an oscillating or semi-oscillating rotor-weight. Synonymous with 'automatic movement'.
Semi-foudroyante Seconds	A complication that is a foudroyante seconds whose rotation cycle is over one second but still under one minute. A semi-foudroyante seconds generally draws less power from the mainspring and still provides far superior legibility of fractions of seconds than a conventional seconds hand.
Semi-oscillation	An action of a balance where the balance wheel will spin either clockwise or counterclockwise. A semi-oscillation is equivalent to a beat, and will trigger the escapement to move and provide input to the rest of the movement. It is called a semi-oscillation because it is movement in only one direction. The following semi-oscillation will occur in the opposite direction, and together the two semi-oscillations will constitute an oscillation.
Serial Number (SN)	A unique alphanumerical designation given to an individual timepiece. Not to be confused with 'reference number', which is an alphanumerical model designation and thus shared by all timepieces of the same configuration. Naturally serial numbers are much longer than reference numbers and are represented on the documentation that accompanies the timepiece. Oftentimes a watch's movement and case will have separate serial numbers.
Serpentine Hands	A style of hands distinguished by a squiggly profile. Also called ‘snake hands’. Serpentine hands are not lumed.
Serti Dial	(French) Rolex nomenclature for a gem-set dial, derived from the French word ‘serti’ meaning ‘gem-set’ (masculine). In the context of Rolex corporate lingo, a Serti dial is any gem-set dial. In the context of watch collecting, a Serti dial is a specific series of gem-set dials where diamonds, rubies, and sapphires replaced the lume plots on the Submariner and GMT-Master IIs of the 1980s to the 2000s. These Serti dials came in either champagne or silver and are seen in Submariner references 16613 and 116613 and GMT-Master II reference 16718.
Service	A term that encompasses all maintenance, repair, cleaning, and correction work done on a watch, especially on the movement. Servicing generally does not refer to cosmetic procedures like polishing.
Setting Lever (keyless works)	A lever connected to the crown stem that moves to mesh the intermediate wheel with the minute wheel when the crown stem is pulled into setting position. It is usually a simple lever with a protruding pin that engages with the detent spring of the cover plate. Not to be confused with the setting lever of a lever-set pocket watch.
Setting Lever (pocket watch)	A lever on lever-set pocket watches that allows the time to be set. The setting lever itself does not set the time, but instead serves as a safety mechanism to prevent accidental resetting of the time.
Seven-segment Display	A system of displaying numbers and some letters and symbols by selectively showing one or more of seven segments rectangularly arranged in a figure eight. The segments are often in the form of elongated hexagons and are typically oblique or slanted to enhance readability. Seven-segment displays can come in both LED and LCD forms. Also see ‘dot matrix display’.
Sex Pile	Watch collecting slang for a group photo of the watches worn by participants of a watch meet-up. The watches are typically laid out on a large table.
Shaped Case	Any case that is not round.
Shark Mesh Bracelet	See 'mesh bracelet'.
Shock Resistance	A timepiece's ability to maintain an acceptable level of performance after mechanical shock. Shock resistance is measured in several ways that involve various surfaces of the watch getting hammered with a plastic mallet and dropped from various heights onto a hard surface. The timepiece is then tested for accuracy and functions afterwards. As the testing is not as straightforward as water or magnetic resistance, the level of shock resistance is usually not displayed in a single unit for the consumer to see. However, internal testing stipulates mallet mass, impact velocity, and/or energy delivered in joules (J). Shock resistance is usually achieved with dampers, jewels, special materials, or sometimes even a whole suspension system.
Shoes	Watch collecting slang for a watch band.
Shogun	(Japanese) A nickname for the Seiko reference SBDC007 diver and the various divers that take after it. The name started as a result of an internet watch forum discussion about the watch where a user declared he would call the SBDC007 the Shogun as it had 'full battle armor' (referring to its special titanium alloy and protective coating), 'crisper lines', and 'always seems to be under attack' (by enthusiasts who believed the watch to be overpriced). Shoguns were influential military dictators who had a considerable impact on Japanese history and culture from the Heian period (8th century) to the Meiji Restoration (19th century).
Shrouded Lugs	See ‘hooded lugs’.
Shunt System	A chronograph control system which manages the operation of the various levers inside a mechanical chronograph mechanism. Shunt systems are also called ‘chronograph control systems’ or ‘chronograph command systems’.
Shuttle Cam	A chronograph control system which utilizes an oscillating cam (also called a ‘shuttle’) to control various levers of a chronograph. The shuttle cam rocks back and forth on its axis unlike the column wheel which turns clockwise in one-click increments. The cam is constructed of two irregularly-shaped cams stacked vertically, with the top cam handling reset and the lower cam handling start/stop. The cam engages the various levers with flat and broad surfaces, which simplifies the operation, reduces the part count, and is more forgiving in its tolerances. Hence the cam is much cheaper to produce, usually easier to repair, and is reputed to be more reliable than the column wheel it intended to replace.
Sidereal Time	Time based on Earth’s rotation relative to the fixed stars, which are stars that despite being mobile, are so far that their movements are imperceptible to the human eye. A sidereal day is approximately 23 hours and 56 minutes and 4 seconds.
Sidereal Time (complication)	An astronomical complication that indicates sidereal time on a dedicated subdial.
Sideshake	The horizontal tolerances of a jewel. Also see ‘endshake’.
Sierra Timezone	Military timezone name for UTC+6.
Sigma Dial	A dial with a symbol that resembles a lowercase sigma of the Greek alphabet. The symbols usually come in pairs and can be found around the five and six o'clock markers. The sigmas indicate that the markers and/or the hands are made of solid gold. This mark was promoted by APRIOR, the Association for the Promotion of the Gold Industry, to advertise that the watch had gold components and was therefore a good buy. This was during the 70s, when traditional watch companies were going under and desperately needed to appeal the value of their products to increasingly uninterested customers. Sigma dials continued limited production by some members of APRIOR until the 1990s. Today they are regarded collectible. Also see 'OM dial'.
Signal Gun	An artillery piece that serves as both a visible and audible time signal. Signal guns fire blank shells to announce a predetermined time such as noon. They were especially common in ports and harbors and served as a time signal to which vessels in port could synchronize their marine chronometers. As sound travels more slowly than light, the sailor would look for the flash and smoke from the gun's muzzle instead of waiting for the blast. While time balls were arguably a more accurate method than signal guns, the guns were superior in low visibility such as fog or haze as they could be heard. Those waiting for the blast referred to tables that showed the precise time the sound would reach each unit of distance from the gun. The signal gun is still in use as a nod to tradition in Hong Kong, Cape Town, Edinburgh, Vancouver, Rome, and other cities around the world.
Signature	The logo of the manufacturer on the dial, usually under the twelve o'clock marker.
Signed	Possessing a signature. Antonymous with 'sterile'.
Silver (Ag)	An element used in the manufacture of watches. Silver is a relatively rare material in watches today, especially compared to the first half of the 20th century when they were a common case material for watches. Today it used as a novelty case material.
Silver-gilt Dial	A galvanized gilt dial that uses a silver or silver-colored substrate, or a dial that has a similar appearance.
Simple Calendar	Any calendar complication that does not have any mechanical memory can be described as a simple calendar. A simple calendar will always progress to the 31st unless corrected manually. The most common simple calendar is the ubiquitous date complication.
Single Red Sea-Dweller (SRSD)	A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 1665 with 'Sea-Dweller' in red ink. An ultra-rare prototype that was never released mass-market, the Single Red Sea-Dweller is one of the most elusive and valuable dive watches in the world. About a dozen examples are known to exist.
Single Roller Escapement	An escapement which utilizes a single roller. The single roller is the most basic configuration and has been replaced with the double roller in many instances. Single rollers can be easily identified by a vertical guard pin and the absence of a safety roller. As there is no dedicated safety roller, the passing hollow for the guard pin is cut out from the rim of the single roller.
Single-fold Clasp	A clasp that opens from only one end.
Sinn	A watch manufacturer established in Frankfurt am Main, Germany in 1961. Sinn is privately owned.
Skeleton	A watch with an exposed movement. Generally a skeleton is any openworked watch with minimal or no dial. In the truest sense a skeleton is an openworked watch with a skeletonized movement. Many skeleton watches are partially see-through.
Skeletonization	The elimination of surface material down to its minimum structural framework. Skeletonization can be executed for aesthetics or weight reduction. Commonly skeletonized parts include hands, bridges, and wheels.
Skeletonized Hands	Hands that are skeletonized. This can apply to almost any style but commonly skeletonized hands include cathedral, syringe, baton, arrow, alpha, sword, and paddle. Hands can be skeletonized for weight reduction or aesthetics. Some special purpose hands are skeletonized for visual distinction from other hands especially if they are mounted onto the same handstack.
Skeletonized Lugs	Lugs that are skeletonized. Typically done for stylistic purposes.
Skindiver	A subcategory of dive watch that is designed for skindiving or free-diving. Skindivers are typically more svelte, smaller, and less water resistant than other classes of dive watches because skindivers do not typically reach the depths, water conditions, or dive times that scuba divers do. Skindivers are appreciated for their more refined looks and smaller sizes. Skindivers today often reflect the designs of the 1960s and 70s when the style was more popular and better known.
Slave Clock	A clock that receives time signals from a more accurate clock serving as a time standard, i.e. a master clock. A slave clock is usually a clock with an independent timekeeping organ that only corrects itself with periodic time signals (e.g. every hour). However, certain slave clocks are but distant displays for the master clock as they are only equipped with a motor that moves with an electrical signal given directly from the master clock. These clocks were ubiquitous in schools, factories, workplaces, train stations, and other facilities where multiple clocks must display the exact same time. The archetypal slave clock which operates through electrical pulses is now antiquated, although clocks synchronized by radio-transmitted time signals from a superior timepiece are just as ubiquitous today. In some situations it may still be appropriate to call these clocks slave clocks.
Slide	A mechanical actuator which is actuated by being slid across the case flank. It is usually in the shape of a curved ramp and is found on the case flank opposite the crown. Slides are used almost exclusively in striking watches to actuate repetition. In many cases, the slide winds the auxiliary mainspring as it is slid across its groove to provide power to the striking mechanism.
Slide Rule	A scale or set of scales that serves as a multifunctional analog computer. Slide rules have existed for centuries in various forms, usually in the more prolific linear form. Circular slide rules provide much more accurate calculations in a tighter package but are also more prone to erroneous calculations from minor misalignments. They are famously used for aviation where they perform calculations for navigation via dead reckoning and other aviation-related computations. Adaptations of the circular slide rule are sometimes mounted on wristwatches and can help with climb/descent rate/time, fuel consumption, fuel unit conversion, airspeed, and distance. These slide rules require a rotating bezel so that the wearer can adjust the outer ring of the slide rule against the inner ring to input values by aligning them to each other. They are mostly found on pilot's watches.
Slide Rule (Seiko)	A nickname for the 6138-700X series automatic chronographs, which feature a pair of slide rule bezels. This makes it capable of performing mathematical calculations. As such, it is also called the ‘Pilot Calculator’.
Sliding Buckle	A type of buckle that clamps down on any point of the strap or bracelet without the need for adjustment holes. Its name comes from how the buckle slides along the strap.
Sliding Pinion	A component of the keyless works that slides in and out of a contact position with other gears of the keyless works. The name is self-explanatory, and the pinion takes the
Sliding Wheel	Any wheel that slides. In a chronograph mechanism, a sliding wheel is a wheel attached to a sliding lever. This can be the coupling wheel which moves as a part of a lateral clutch system or the intermediate wheel which connects the chronograph runner and minute recording wheel. The latter use is more common as the former is more commonly referred to as the coupling wheel.
Sliding/Intermediate Lever	A component of a chronograph mechanism which pivots to engage and disengage the intermediate wheel from the chronograph runner’s finger.
Sliding/Intermediate Wheel Spring	A component of a chronograph mechanism which applies constant pressure to the intermediate lever.
Small Seconds	A type of seconds hand whose range of movement occupies a dedicated sub-dial instead of the entire area of the dial. Small seconds sub-dials are usually located at the six o'clock position. They typically declutter the dial from the movement of the seconds hand at the expense of some legibility. Small seconds used to be the norm because the position of the third wheel (which is connected to the escapement) on which the seconds hand is mounted is naturally off-center. Due to the proliferation of 'direct center seconds', some small seconds are sometimes seen as a complication due to the extra gearing now required to display the seconds off-center.
Smooth Balance	A balance wheel with completely smooth surfaces, lacking timing screws, cams, inertia weights, and cuts. Some have minor indentations and dimples. Smooth balances are poised from the factory with any extra adjustments done by adjusting the length of the hairspring through a regulator.
Smurf	A nickname for the Rolex Oyster Perpetual Submariner reference 116619LB, a Submariner with a blue Cerachrom bezel, blue lacquer dial, and gray gold case released for the centennial anniversary of the 'Rolex' name and 55th anniversary of the Submariner. The name comes from the Smurfs, a Belgian comic franchise featuring blue characters.
Snail Cam	A cam that is shaped like a snail shell or comma. Used for several watch components, especially snail cam regulators.
Snail Cam Regulator	A regulator that utilizes a snail cam to adjust the index lever. The snail cam regulator is designed to make finer adjustments.
Snail Scale	A scale, usually at the center of the dial, that is the shape of a logarithmic spiral. A snail scale declutters the dial by moving a scale away from the rim of the dial. It is useful in multi-scale chronographs and commonly feature a tachymeter as it is a logarithmic scale.
Snap-on Caseback	A type of caseback that is fastened by air pressure. They are also called snap backs. Snap-on casebacks simply require a push by the thumb to seat it into place. They may be opened with a thin bladed opening tool, pocket knife, or cheese knife. Snap-on casebacks provide no impressive resistance against the elements but are thin, elegant, and simple and are just fine for the average day.
Snoopy	A nickname for the Omega Speedmaster Professional chronographs that celebrate Omega’s recipiency of NASA’s Silver Snoopy Award in 1970. The first Snoopy was released in 2003 as ref.3578.51.00.
Snowflake	A nickname for the Grand Seiko reference SBGA011/211 and the Tudor Prince Oysterdate Submariner references 7016/0, 7021/0, 9104/0, and 9411/0. The two watches are very different, the former dubbed 'Snowflake' for its snowy dial texture and the latter for its angular hands and indices that resemble snowflakes.
Snowflake Dial	A dial with snowflake indices. A variation of diver indices, snowflake indices are composed of an isosceles triangle at twelve, rectangles at three, six, and nine, and squares for the rest. Snowflake dials are usually paired with snowflake hands.
Snowflake Hands	A diver handset with blocky and angular profiles. The hour hand is a baton-style hand ending in a rhombus or a titled square. The minute hand is a regular baton hand and the seconds hand is a lollipop-style hand with a tilted square instead of a circle. Snowflake hands are usually paired with a snowflake dial.
Sodalite	A deep royal blue mineral with white and cream marbling, often used as a gemstone. In watchmaking, sodalite is a rare dial material used by Rolex for select Datejust, Day-Date, and Daytona references in the 1990s to the 2010s.
Solar Cell	See ‘photovoltaic cell’.
Solar Watch	A watch with a light-powered movement.
Solar-powered Movement	See ‘light-powered movement’.
Soldered Lugs	Lugs which have a clear and visible soldering line between the base of the lug and case, or any lugs that are attached through soldering regardless of visibility. Soldering is a metal-joining technique that uses a molten filler metal called a solder to conjoin two workpieces without having to melt the work pieces like in welding. Soldering was common in the earliest era of wristwatches in the late 19th and early 20th centuries when wire lugs were being attached to pocket and pendant watch cases. It seems to have fallen out in favor of brazing, which operates at a much higher temperature and allows for finer fitting of the work pieces. Soldering as a technique is still common for DIY/garage jobs and for fixing bars onto lugs. Also see ‘brazed lugs’ and ‘welded lugs’.
Solid Caseback	A caseback that is made of solid metal.
Solid End Link	An end link that is constructed of a solid block of metal. Solid end links are heavier than their hollow components but are sturdier. Also see 'hollow end link'.
Solo (Rolex)	A nickname for examples of the Rolex Cosmograph Daytona references 6239 and 6240 which feature only one line of dial text: the Rolex signature.
Sophia Loren	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 16760, a GMT-Master II with a black and red aluminum bezel and red GMT hand. The name 'Sophia Loren' (a voluptuous Italian actress) is a reference to the beefy case that was needed to accommodate the upgraded movement, which was the first iteration of the GMT-Master II that could display one more timezone than the GMT-Master and had an independently-adjustable hour hand. The watch was also dubbed the 'Fat Lady' for the same reason and the 'Coke' for its colors.
SOTC	'State of the collection'. Watch collecting slang for a photo or video that shows the current status of a watch collection.
Souscription	(French) Subscription.
Southpaw	A nickname for a watch whose crown is on the left side of the case as opposed to the typical right side. Other nicknames include ‘destro’, ‘LHD’ and ‘lefty’.
Space Watch	A category of wristwatch designed for use by astronauts in space. Space watches can come in many forms but most have some sort of timing function that measures total mission elapsed time (MET) or a single session of extravehicular activity (EVA). Some are designed to display multiple timezones for tracking mission control time and home time. Space watches usually come on super long velcro straps to fit over spacesuits and usually use high-performance quartz movements with digital or hybrid displays.
Spade Hands	A style of hands distinguished by a spade tip. The body of a spade hand is usually tapered from a wide base to a thin neck. Spade hands are typically not lumed.
Spade-and-whip Hands	A style of hands distinguished by a spade-shaped hour hand and whip-shaped minute hand. Spade-and-whip hands are typically not lumed.
Speed	A colloquial term for the frequency of a mechanical movement. A fast movement is typically one that has a high beat rate, while a slow movement typically has a low beat rate. Speed may also be used to describe a movement’s current frequency in comparison to its optimal frequency - a movement that moves fast will likely gain time (run faster than it should) and a movement that moves slow will likely lose time (run slower than it should).
Speedy	A nickname for the Omega Speedmaster family of watches.
Speedy Tuesday	A social media trend started in 2012 by Fratello Watches, a The Hague-based watch media company. The trend started as a hashtag on Facebook and later Instagram, usually posted on Tuesdays along with a photo of an Omega Speedmaster. It was the first major movement associating a day of the week with a certain watch and inspired several similar trends. Omega picked up on the trend and has released several Speedy Tuesday limited editions since 2017 to reciprocate to the community.
Spider Dial	A dial with cracked lacquer. Used in Rolex nomenclature to refer to Rolex's first glossy dials for the Submariner rolled out in the 1980s which had a lacquering defect that caused cracks. This so-called 'crazing' is relatively faint and does not chip off. While some appreciate these dials for their mosaic-like appearance, many others simply view it as glorified damage.
Spider Lugs	A style of lugs whose outer profile tapers outward and back inward. The inner profile can either be straight or follow the outer profile. The latter overlaps with a certain style of crab lugs. The name comes from how the lugs resemble the legs of a spider.
Split Balance Wheel	See 'bimetallic balance wheel'.
Split Grain Leather	A type of leather. Split grain leather comes from the reticular portion of the animal hide, making it more pliable and softer than cuts from the papillary portion. It is better known by the name 'suede'. It provides a velvety smooth texture, extra comfort on the wrist, and a soft aesthetic. It is not durable or water resistant when compared to leathers made from the top layers.
Split Pusher	A pusher on a split-seconds chronograph that splits the two overlapped chronograph seconds hands, stopping one at the time of split and allowing the other to progress with timing. Pushing the split pusher a second time will launch the split hand to catch up with the running hand.
Split-seconds Chronograph	A chronograph that is capable of recording two separate events that start at the same time but end at different times. This is achieved by having two perfectly-overlapped chronograph seconds hands which start together when the chronograph is actuated. When the split pusher is actuated, the hidden chronograph seconds hand stops in its place while the top hand continues around the dial. When the second event has ended, the top hand can be stopped via the start/stop pusher and the wearer can determine the elapsed time for both events as well as the time between the two events as long as the difference is under a minute. The bottom hand or splitting hand can also be recalled while the chronograph is in motion by simply pushing the split pusher once again. This earns the complication its French name ‘rattrapante’, or ‘to catch up’. Naturally, a split-seconds chronograph typically has three pushers (start/stop, reset, split) and can be identified by them. The split-seconds chronograph is regarded as high complicat
Spork	A nickname for the Seiko SRP043K series diver. There are two possible origins for the nickname. The first is that the reference number 'SRP043K' looks like the word 'spork'. The second is that the watch is a combination of a pilot's watch (dial) and a dive watch (case) like a spork is a combination of a spoon and fork.
Sports Watch	A category of wristwatch designed for activity. The sports watch is likely the broadest category of watch, especially as it has replaced the dress watch as the default style in today's more casually-dressed society. Any watch designed for an active purpose may technically be called a sports watch, but the term usually refers to a watch with no specific/professional purpose in mind other than a generally active lifestyle. This makes sports watches ideal daily watches and all-rounders that go along with a wide spectrum of clothing and fit as much in an office as they do at a beach.
Spring Bar	A type of bar that is fitted between the lugs using a spring-loaded retractable head. The spring bar is the most common bar type. The vast majority of spring bars have a retractable head on both ends. Spring bar heads usually have a shoulder that the forked end of a spring bar tool can access to pull back the head during a strap change.
Spring Bar Pliers	A pair of spring-loaded pliers that are used to remove a spring bar from a watch by pinching the two heads in simultaneously. The tips of the pliers are forked to engage the shoulders of the spring bar. Spring bar pliers are typically better for removing spring bars than spring bar tools as they are faster, more precise, and minimize the risk of the spring bar head scratching the inside of the lug as it is dragged out. They are also useful for engaging bracelets with small openings for the spring bar heads such as the notoriously tricky modern Rolex bracelets.
Spring Bar Tool	A type of strap tool that is designed to attach and detach a spring bar from a pair of lugs. A spring bar tool is often double-ended, with one end fitted with a narrow push pin for pushing the retractable head out through a drilled lug and the other fitted with a forked end for pulling the shoulder of the spring bar. As the spring bar tool is the most common type of strap tool, two terms are sometimes used interchangeably.
Sprite	A nickname for the Rolex Oyster Perpetual GMT-Master II reference 126720VTNR, a GMT-Master II with a black and green Ceramchrom bezel, green GMT hand, and a left-hand crown. The name is a reference to the green color of the bezel. However, the watch is known by a couple other nicknames including 'Destro'.
Spur Gear	A type of gear that resembles a spur, consisting of a circular cross section with radially-projecting teeth. It is the best-known archetypal gear. In watchmaking, the vast majority of gears are spur gears with some exceptions.
Square	A nickname for the Casio G-SHOCK 5000 series watches. The name refers to the pronounced rectangular profile of these watches.
Square Case	A case shape distinguished by a square or roughly square profile. Also called a carré case.
Squelette	(French) Skeleton.
Stackfreed	A spring-loaded cam that evens the force output of an unwinding mainspring. The stackfreed was an early attempt at a constant force mechanism. It worked by having a long spring arm bent along the curvature of the movement with a small roller at the end which pushed against a snail cam connected to the mainspring barrel via meshing gears. Essentially the spring’s retarding force on the cam would decrease as the cam rotates to its thinner section, which corresponded with the end of the mainspring’s power reserve. Thus the greater resistance when the mainspring is most powerful and the lesser resistance when it is almost unwound would even out the output of the mainspring. The stackfreed was a high-wear, high-maintenance mechanism that was prone to breakage as it required a strong spring arm and even stronger mainspring to push through the resistance applied by the stackfreed. It was eventually replaced by the fusée-and-chain mechanism which was bulkier but mechanically superior.
Stainless Steel	An alloy often used in the manufacture of watches. Abbreviated Ss, usually referred to simply as 'steel'. As an iron-based alloy that incorporates chromium, nickel, and/or carbon, stainless steel is highly corrosion resistant and rust resistant, has a fine luster, and is hard and durable. It is perhaps the most commonly used material in watchmaking especially for cases and bracelets.
Stamping	A metalworking technique that involves the pressing of a flat metal workpiece into a desired shape. Stamping is a relatively simple and inexpensive process that produces lightweight products quickly and efficiently. It is appropriate for metal components that do not have to be solid metal as stamped pieces are inevitably limited to the thickness of the initial flat workpiece. It is commonly used for bracelet links and clasps, particularly in older or affordable timepieces.
Star Wheel	A wheel (gear) with multiple large leaves (teeth) that make it look like a star.
Starbucks	A nickname for the Rolex Oyster Perpetual Submariner reference 126610LV, a Submariner with a green Cerachrom bezel and black dial. The name is a reference to the green color of the Cerachrom bezel, which is closer to a hunter green than the lime green of the similar Kermit. As it is technically a successor to the Kermit but with a ceramic bezel, the reference also has the nickname 'Cermit'. Some collectors use Starbucks to refer to the 126610LV produced from 2020 to 2023 and Cermit to refer to those produced 2023 onwards due to the more lime-like color of the new bezel. Also see 'Cermit'.
Starfish	A nickname for the Seiko reference SGT234P and the SKZ28X series divers that each have a radically scalloped bezel with six points that resembles a starfish.
Stargate	A nickname for the Seiko reference SZK325K diver and the various divers that take after it. The name comes from the large inverted trapezoidal protrusion on the bezel that resembles the portals in the 1994 film Stargate.
Start/stop Pusher	A pusher on a chronograph that starts and stops the operation of the chronograph.
Stella Dial	The name of a series of lacquered enamel dials produced for the Rolex Day-Date in the 1970s. The name 'Stella', whose etymology is unclear, is not a nickname but rather an official designation by Rolex.
Stelline	(Italian) Little star. A nickname for certain examples of the Rolex Oyster Perpetual reference 6062 Triple Calendar which feature hour markers in the shape of five-pointed stars. Also see 'Galaxy', a ref.6098 with the same indices.
Stem	See ‘crown stem’.
Step Motor	A motor that moves in steps. Also known as 'stepping motor' and 'stepper motor'. The step motor is the most common type of motor in quartz watches, of which the Lavet-type step motor is the most common. The step motor is responsible for the ticking of the seconds hand in a quartz watch.
Stepped Case	A case that that has a stepped or tiered bezel. Stepped cases typically have flat surfaces but some are rounded.
Stepped Lugs	Lugs that have stepped flanks.
Sterile	Bearing no written markings or logos, especially the manufacturer signature. Usually refers to the dial.
Steve Jobs	A nickname for the Seiko Chariot reference 6431-6030 worn by Apple Inc. co-founder Steve Jobs as well as its modern reissues in the SCXP0XX series.
Steve McQueen (Heuer)	A nickname for the Heuer Monaco reference 1133B automatic chronograph. While ‘Steve McQueen’ is sometimes used to refer to the entire Monaco range including the modern TAG Heuer Monacos, in the purest sense it refers only to the original Monaco worn by American actor Steve McQueen.
Steve McQueen (Rolex)	A nickname for the Rolex Oyster Perpetual Explorer-II reference 1655. Despite virtually no connection between the American actor Steve McQueen, the watch is still associated with him. Other, more apt nicknames for the 1655 include the Italian 'Freccione'.
Stitching	Lines of thread sewn into the sides of a strap to adhere its components together. Stitching done in a markedly different color from the strap is called 'contrast stitching'. Two lines of stitching on each side instead of the conventional one is called 'double stitching'.
Stop/Hacking Seconds	The ability to stop the seconds hand when setting the watch. Sometimes considered a complication. Also see 'hacking'.
Stopwork	A system that limits the extent to which a mainspring barrel can be wound. This not only prevents overwinding but more importantly prevents the mainspring from operating at the peak of its torque curve. This keeps the mainspring in its optimum operating range when the torque is proportional to the angle of rotation. This is when it follows Hooke’s law (see ‘Hooke’s law’). Moreover, a stopwork can protect the escapement from overbanking, which is when the high amplitude from a high torque output over-swings the balance and makes the impulse pin strike the outside of the lever. The most common style of stopwork is the Geneva stopwork.
Stormin' Norman	A nickname for the Seiko reference SKX009 diver famously worn by United States Army General Norman Schwarzkopf Jr. also known as Stormin' Norman. The watch was almost always on Schwarzkopf's wrist and publicized heavily by the press.
Stowa	A watch manufacturer established in Hornberg, Germany in 1927 and now headquartered in Engelsbrand, Germany. Stowa is privately owned.
Straight Lugs	A style of lugs that are roughly straight with minimal or no taper. There is a clear demarcation between the case and the lugs as they protrude abruptly.
Straight-end Bracelet	A bracelet that is connected to the lugs via a straight bar instead of end links. The bar prevents a flush fit to most cases unlike end links, leaving a lot of room between the bracelet and case. However, this allows the bracelet to fit on virtually any watch.
Strap	A band made of leather, fabric, or rubber.
Strap Monster	A watch that looks good with a wide range of straps.
Strap Tool	A tool for attaching and detaching bands from wristwatches. Strap tools are typically fitted to address the two main types of bars: spring bars and screw bars. They are also capable of resizing bracelets. A tool may have a push pin, forked end, or a screwdriver bit. Many tools are double-ended and come with ruler markings on the shaft for easy measurement of the lug width.
Strike Sequence	The particular order and composition of strikes which conveys information or a melody.
Striking Complications	A family of complications that concern the announcement of time through sound. Striking complications make up some of the most coveted complications, spanning from the relatively simple alarm to the high complication that is the minute repeater.
Striping	A finishing technique where an abrasive tool grinds semicircular patterns in broad lines onto a surface. Usually the lines are parallel to each other and unidirectional. However, radial striping is not uncommon. The technique is usually employed for stationary structural surfaces such as plates and bridges. It is also common on oscillating masses on automatic movements. Striping is also known as 'Geneva striping' or 'Côtes de Genève'.
Stripping	Damage to threading, usually in the form of being stripped off. Stripping is typically a consequence of cross-threading.
Strontium (Sr)	An element that is sometimes used as the frequency reference in atomic clocks.
Strontium Aluminate	A non-radioactive, biologically and chemically inert compound that is used for lume. Normally in powder form, it is used as an ingredient for photoluminescent afterglow paint. Strontium aluminate-based lume is photoluminescent, which means it must first absorb photons to excite the paint. Thus, these paints will completely lose their luminescence after a certain period in darkness. Strontium aluminate is the most commonly used compound for modern day lume.
Stud	A piece of metal that fastens the outer end of the balance spring to the balance cock.
Sub-register	Synonymous with ‘subdial’. In common parlance, ‘sub-register’ seems to be more commonly used when describing chronograph subdials, but the two terms are interchangeable.
Subdial	A separate, usually circular area within a dial that displays information with a hand or pointer and a track or scale. A subdial is almost never concentric with the dial but instead offset at one or several of the four cardinal directions. There are no rules as to where a subdial must be placed or how many there may be. They are most commonly found on watches that display information other than the time, i.e. watches with complications. However, some watch layouts like regulators delegate the display of each unit of time to a separate subdial.
Submarine Steel	A type of steel used in the manufacture of submarines but also wristwatches. Typically refers to HY-80 or HY-100 steel. Submarine steel is a low carbon steel that uses far more iron than its stainless steel counterparts followed by modest amounts of nickel and chromium. It contains higher carbon content than 316L steel and may include titanium and vanadium. The alloy is then quenched and tempered resulting in a material that offers excellent yield strength, impact resistance, hardness, and good corrosion resistance and ductility. Other than submarine hulls and wristwatch cases the metal is also used for armor plating, construction vehicles, and heavy duty industrial equipment.
Subscription Watch	A watch that is payed for on a so-called subscription plan. Usually the subscription plan is a down payment of a fraction of the watch’s total value for an allotment. Subscription watches have existed since at least the time of Abraham-Louis Breguet, whose subscription payment plan offered a guarantee of delivery upon initial down payment of a quarter of the watch’s total value. This allowed him to expand his clientele to those who could not afford to pay for the watch in lump sum. Subscription models are also used to secure initial capital for fledgling watchmakers.
Subseconds	Synonymous with ‘small seconds’.
Suede	See 'split grain leather'.
Sumo	(Japanese) A nickname for the Seiko SBDC001 and the various divers that take after it. The name has a couple possible origins, the first being the noticeably large and stout profile of the watch, reminiscent of a sumo rikishi. Another is the shape of the twelve o'clock marker which is said to resemble a mawashi, the loincloth worn by sumo wrestlers. Some say that the marker also resembles the ōichō-style chonmage (topknot) worn by the wrestlers.
Sunburst	A finishing technique similar to brushing where the wire brush abrades the surface of metal to create lines emanating from a single point, usually the center of the finished surface. Sunburst finishing is most commonly used on dials.
Sundial	A timepiece that tells the time with a shadow cast by the sun as it moves through the sky.
Sunrise	A nickname for the Seiko references 6139-6002 and 6139-7060 featuring an extra graduated ring outside the subdial. This so-called ‘sunrise’ ring is colored red from 0 to 10 on the teal dial 6139-6002, hence the name.
Super Compressor Case	A type of dive watch case whose caseback is sealed increasingly tighter by water pressure. Super compressor cases use spring-loaded casebacks that only become as watertight as they need to be. This reduces wear on the components. Super compressors are distinguished from the compressors with their screw-down casebacks, which were more watertight than the compressors' snap backs. However, several were mounted with bayonet casebacks. Also see 'compressor case' and 'compressor'.
Surprise Piece	A component of a repeater which lies underneath the quarter and minute snails as a safety mechanism. This is important as the quarter and minute snails are directly attached to the cannon pinion and become more susceptible to some sort of failure at the beginning of each hour (for the quarter snail and rack) and each quarter (for the minute snail and rack). First, the surprise piece prevents the complex mechanisms of a repeater from jamming at the cannon pinion due to faulty rack movement. Second, it prevents the feeler from engaging the last level of the snail when it should engage the first. The surprise piece achieves this by acting as an enlarged ramp for the feeler to latch onto the first level and preventing it from reaching the last level. When it has fulfilled its job, the surprise piece is effectively hidden to make way for the feeler as it progresses to the last level of the snail until it redeploys at the start of each hour or quarter. The name comes from how it is hidden most of the time.
Surprise Piece Actuating Lever	A lever which actuates the surprise piece. Also called a flirt. The lever is a gently curved S-shaped level that typically runs from its pivot near the crown stem assembly to the cannon pinion. It either holds the surprise piece or pushes it into position.
Swan Neck Regulator	A regulator that utilizes an S-shaped curved piece of tensile metal (the swan neck) to adjust the index lever. An improvement on the Bosley regulator, the swan neck regulator features a Bosley-style index lever that is pushed on one side by an adjustable screw and the other by the swan neck. The swan neck provides constant tension on the index, allowing for microadjustment using the screw and preventing the index from dipping to one side in the event of a shock. The swan neck regulator is also called the 'whiplash regulator' or 'Reed's regulator' after its inventor.
Swiss (Rolex)	A marking that indicates the Swiss origin of a Rolex watch, found at the classic six o’clock position. ‘Swiss’ in lumed Rolex watches produced before the early 1960s indicates the presence of radium lume as tritium dials have ‘T’ markings. In the post-tritium era which started in 1998 with the introduction of the first photoluminescent lume called LumiNova, Rolex dropped the T and just printed ‘Swiss’ on the dial as there was no longer tritium. These dials are called ‘Swiss-only dials’ and are rare as Rolex started using ‘Swiss Made’ in 2000 with the introduction of Super-LumiNova.
Swiss Cottage Industry	A name for the decentralized style of home-based watchmaking that dominated the Swiss watchmaking industry during the 18th and 19th centuries before industrialization. Many former textile workers who became unemployed took up fashioning simple components in their homes with their families, and the network that connected all these disparate manufacturers into an assembled final product became known as ‘établissage’.
Swiss Lever Escapement	Also called 'inline lever escapement'. The Swiss lever escapement is the most widely used variety of the lever escapement. It assembles the balance, lever, and escape wheel in a roughly straight line (hence 'inline') unlike the English system where the balance and escapement are perpendicular to each other. While the components are identical, their shapes are not. Swiss levers have the now-ubiquitous T-shaped profile and escape wheels have club-shaped teeth.
Swiss Made	An origin marking indicating that the product originates from Switzerland. The criteria for what can be officially marked Swiss Made is determined by ordinance. As of time of writing, a watch may be marked Swiss Made if its technical development was carried out in Switzerland, the movement is Swiss (see 'Swiss movement'), the movement was cased in Switzerland, the final inspection was done in Switzerland, and at least 60% of the manufacturing costs were incurred in Switzerland. Also see 'Swiss movement' and '60% rule'.
Swiss Made (Rolex)	A marking that indicates the Swiss origin of a Rolex watch, found at the classic six o’clock position. ‘Swiss Made’ in lumed Rolex watches produced before the early 1960s indicates the presence of radium lume as tritium dials have ‘T’ markings. The T-marked dials were replaced by simple ‘Swiss’-marked dials in 1998 with the introduction of the non-radioactive LumiNova, but were quickly replaced in 2000 by Super-Luminova which also ushered in the ‘Swiss Made’ mark. Even after 2008 when Rolex’s proprietary Chromalight took over, the ‘Swiss Made’ mark remained.
Swiss Movement	An origin marking indicating that a watch movement originates from Switzerland. The criteria for what can be officially marked Swiss Movement is determined by ordinance. As of time of writing, a movement may be marked Swiss (and display 'Swiss Movement' on the dial) if it was developed in Switzerland, assembled in Switzerland, inspected in Switzerland, 60% of manufacturing costs were incurred in Switzerland, and if the Swiss-made components constitute 50% or more of the total cost of components of the movement (excluding assembling costs). Also see 'Swiss made' and '60% rule'.
Swiss T 25	A marking indicating that the wristwatch’s total tritium emits less than 25 millicuries.
Swiss T < 25	A marking indicating that the wristwatch’s total tritium emits less than 25 millicuries. It is a particularly significant marking for dating and categorizing Rolex watches, on which it is printed at the six o’clock position. This was first done for compliance with the Nuclear Regulatory Commission’s new regulations that exempted licenses for timepieces with under 25 mCi of tritium (among many other specific regulations). Also see ‘exclamation point dial’ and ‘underline dial’, two similar indications of radioactive material.
Swiss-only Dial	A Rolex dial with ‘Swiss’ as its origin marking and LumiNova photoluminescent lume. The Swiss-only dial is relatively rare as it was only produced from about 1998 to 2000, between the uses of tritium and Super-LumiNova. Much earlier dials produced before around 1963 (which, if lumed, have radium) also may have ‘Swiss’, but these typically are not called Swiss-only dials.
Sword Hands	A style of hands distinguished by a gradual taper from a skinny base to a broad shoulder and a rapid taper from the shoulder to the tip. The hands resemble a cartoon European sword. Swords hands may be lumed or unlumed. Lumed sword hands are typically much wider and are commonly used in military watches from the 1950s onwards.
Symmetrical Tooth Profile	Two gear tooth profiles in a single tooth cross section that are symmetrical to each other. Most gears are symmetrically-profiled.
Syringe Hands	A style of hands distinguished by a thin base and straight wide body which radically curves into a long and thin pointer tip that makes the hands resemble syringes. Syringe hands can be understood as wider pencil hands with a pointer tip. They are typically lumed.
T	Tritium. A radioactive isotope of hydrogen that is used as lume. A watch that uses tritium lume will most likely have the letter T emblazoned somewhere on the dial.
T (Rolex)	Trou Borgne. Rolex nomenclature for a blind hole.
T Swiss Made T	A marking that (probably) indicates that the wristwatch’s total tritium emits less than 7.5 millicuries. In the context of Rolex watches, there is an understanding that it also indicates that the indices are made of gold, which is likely not entirely true due to several references having both steel indices and this marking. This marking is often compared to its contemporaries, namely ‘T Swiss T’ and ‘- T Swiss Made T -’. The exact differences are poorly understood, with conflicting information from various sources and no official statement from Rolex. The tentative consensus seems to be that the variation is a result of a lack of standardization, which is a common theme in Rolex watches before the 1990s.
T Swiss T	A marking that (probably) indicates that the wristwatch’s total tritium emits less than 7.5 millicuries. In the context of Rolex watches, there is an understanding that it also indicates that the indices are made of gold, which is likely not entirely true due to several references having both steel indices and this marking. This marking is often compared to its contemporaries, namely ‘T Swiss Made T’ and ‘- T Swiss Made T -’. The exact differences are poorly understood, with conflicting information from various sources and no official statement from Rolex. The tentative consensus seems to be that the variation is a result of a lack of standardization, which is a common theme in Rolex watches before the 1990s.
Tachymeter	A scale that measures the frequency of an event over a second-defined (i.e. under a minute) period. The most common usage of the tachymeter is the measurement of average speed over a known distance, such as a straightaway in a racing circuit or a quarter/half-mile drag race. The units of measurement do not matter as long as they are consistent. Tachymeters can also be used to calculate how many actions one can do in an hour, provided that each action takes less than 60 seconds. As they are so versatile the math used in a tachymeter (T=3600/t, T = tachymeter value and t = elapsed seconds) is applied in many other scales. Tachymeters are frequently featured on the bezel or the outer periphery of a dial. Sometimes they come as snail scales in the center of the dial. Due to their association with racing tachymeters are often featured on racing watches even if no one ever uses them. They must be accompanied by some sort of chronograph that allows the wearer to start, stop, and reset the seconds hand at will.
Tachymeter Bezel	A bezel with a tachymeter scale. Typically, a watch with a tachymeter also has a chronograph complication. In this case, the tachymeter bezel is stationary. In some rare instances where the watch does not have a chronograph, a turning tachymeter bezel allows the wearer to align the start of the tachymeter to the seconds hand.
TAG Heuer	A watch manufacturer established in Saint-Imier, Switzerland in 1860 as Heuer and bought by the TAG group in 1985. TAG Heuer is owned by LVMH Moët Hennessy Louis Vuitton.
TAI	(French) Temps atomique international (International Atomic Time). TAI is an atomic continuous time standard that tracks the flow of proper time. It is a weighted average time of 450 atomic clocks around the world, with a second measured as defined by the International System of Units (SI) using the caesium 133 atom and a single TAI day consisting of exactly 86,400 (24hrs x 60min x 60sec) of those seconds with no exception, i.e. no leap seconds. As TAI is irrelevant to the rotation of Earth, it is not a solar time (unlike UT1 and GMT), and as it is not a conventionally used civil time reference, it is continuous (unlike UTC, which is discontinuous and requires leap seconds to be similar to solar time like UT1). TAI is therefore not ideal for use by laymen or by navigators or astronomers who need a time standard tied to the Earth's rotation. In a sense, TAI is 'true time' as it simply measures the passage of time uninterrupted, whereas solar times like UTC/UT1 are records of Earth's revolution and rotation.
Tang	See 'pin'.
Tang Buckle	See 'pin buckle'.
Tango Timezone	Military timezone name for UTC+7.
Tank	A rectangular case or a watch with such a case. 'Tank' is a proprietary eponym that is genericized from the Cartier Tank of 1917. Cartier's Tank took the name from the armored vehicle, namely the Renault FT light tank that inspired Louis Cartier to design the watch. Due to the iconic status of the Cartier Tank, 'tank' has become a byword for any similar rectangular watch.
Tantalum (Ta)	An element used in the manufacture of watches. Abbreviated Ta. Tantalum is blueish gray in color, extremely hard, ductile, and highly corrosion resistant. It is rarely seen in watchmaking and when used, commands prices prohibitively high for most. Tantalum can be seen as case and bracelet material in certain pieces.
Taper	The diminishment in width from one extremity to the other. Normally used to describe the dimensions of straps as tapered straps need separate measurements for the lug width and buckle width. Taper is also used to describe the beautiful contours on a watch's head such as the lugs or case flanks.
Tapered Lugs	A style of lugs that taper in width, typically having a wide base and a narrow tip.
Tasti a Spillo	(Italian) Pin button. A nickname for the small pushers that can be seen on many chronographs from Longines, Vetta, Zenith produced from the 1940s to 1960s.
Tasti Tondi	(Italian) A nickname for the Patek Philippe reference 1463 chronograph. It is Patek Philippe's first waterproof chronograph. The nickname, Italian for 'round buttons', is a reference to the waterproof pump pushers. The Tasti Tondi can be identified by pump pushers with radially fluted surfaces.
Tavannes	A watch manufacturer established in Tavannes, Switzerland in 1891. Tavannes is privately owned.
TBR	Tessellate Brillants. Rolex nomenclature for a watch with thirty-six baguette cut diamonds on the bezel and diamond-paved dial..
Teardrop Lugs	A style of lugs that resemble a drop of water, with one bulbous end and one sharp end. Typically the sharp end is attached to the case while the bulbous end holds the bar. However, this configuration is often reversed. In this case, teardrop lugs are very similar to horn lugs and are the terms are used interchangeably.
Telemeter	A scale that measures the distance between the observer and a phenomenon/object based on the disparity between the speed of light and speed of sound. Simply put, it is a scale that does the same job as claps between the strike of lightning and the sound of thunder to determine how far away the storm is. Telemeter scales were particularly useful for infantry and artillery officers as they could determine the distance to enemy gun positions. Unlike most scales, the telemeter is a linear scale. Like most scales, telemeters are marked at the outermost periphery of the dial and must be accompanied by some sort of chronograph that allows the wearer to start, stop, and reset the seconds hand at will.
Telemeter Bezel	A bezel with a telemeter scale. Typically, a watch with a telemeter also has a chronograph complication. In this case, the telemeter bezel is stationary. In some rare instances where the watch does not have a chronograph, a turning telemeter bezel allows the wearer to align the start of the telemeter to the seconds hand.
Telephone Dial	A dial with numerals contained within circles, resembling the numbers on a rotary dial telephone.
TEM	Tessellate Émeraude. Rolex nomenclature for an emerald-set watch.
Tensoku	(Japanese) Short for 'Tentai Kansoku Dokei', or 'Astronomical Observation Watch'. Refers to the Seikosha Tensoku, a pilot's watch made for aviators of the Imperial Japanese Armed Forces during WWII. The watch is strongly associated with the Mitsubishi A6M Zero, the primary fighter aircraft of the Imperial Japanese Navy Air Service. For this reason it is also known as the 'kamikaze watch', even though there is no direct connection between the watch and the kamikaze suicide attacks. See 'Beobachtungsuhr' for comparison.
Terminage	(French) The final steps of creating a watch, which include assembling finished components, testing and timing the movement, and fitting hands and casing. This task may be delegated to an atelier de terminage.
Termineur	(French) An individual or workshop which engages in terminage.
Texas Timex	A nickname for the Rolex Oyster Perpetual Day-Date in yellow gold, as well as the similar-looking Datejust in yellow gold. The name comes from 1970s Texas, where the yellow gold Day-Date was so popular among the wealthy that it was metaphorically as common as a Timex (an affordable and widely worn American brand). This was popularity was likely kickstarted by the widely televised Day-Date worn by President Lyndon B. Johnson (a Texan himself). Texas in the 70s enjoyed mass industrialization, urbanization, and an influx of talent from out of state which created a large wealthy class who could afford a Day-Date. When the Day-Date could not be had, Texans opted for the similar Datejust.
THA	Techniques Horlogères Appliquées. A company that specialized in the production of mechanical movements, especially those with complications. The company was founded by Vianney Halter, François-Paul Journe, and Denis Flageollet who each went on to found respected independents Vianney Halter, F. P. Journe, and De Bethune. Founded in 1989 in Sainte-Croix, Switzerland, the company was bought by Bucherer in 2007 which was acquired itself by Rolex in 2023.
Thickness	A commonly used alternative for 'height'.
Third Party	Executed by an external company. The term has no clear standard as to what it means. In common usage, 'third party' is largely synonymous with 'outsourced' and 'ébauche'. However, the latter term can only be used for movements.
Third Party Movement	A movement made by another watch manufacturer. Refer to 'ébauche', which is usually an interchangeable term. In some use cases, a third party movement is different from an ébauche movement in that ébauche movements usually refer to blank movements made by ébauche watchmakers whereas third party movements may denote a manufacture movement that was sold to another brand. This distinction is not very important. See 'ébauche', 'in-house movement', and 'proprietary movement' for comparison.
Third Wheel	A component of the going train that is the third wheel to transfer energy from the unwinding of the mainspring. A coaxial pinion meshes with the second wheel, turning the third wheel which in turn moves either the fourth wheel (if the watch has a seconds display) or the escape wheel (if the watch does not have a seconds display). The third wheel is an intermediary wheel and does not control any dial-side activity.
Thomas Earnshaw	(1749-1829) A horologist from Ashton-under-Lyne, England and active in London. Earnshaw is credited with improving the bimetallic compensation balance and spring detent escapement. He was also noted for his fine workmanship which made him an escapement specialist.
Thomas Mudge	(1715-1794) A horologist from Exeter, England and active in London. Mudge is credited with the invention of the lever escapement - possibly the single most influential mechanical innovation in the past three centuries of horological history - along with various improvements to marine chronometers. It is likely that Mudge also created the first watches with equation of time, gear-train remontoir, and even the perpetual calendar.
Threading	The process of creating a helical groove or ridge called a thread, or the thread itself. In watchmaking, threading is almost always used as a fastening mechanism especially for components that need to be watertight such as crowns and casebacks in water-resistant watches.
Three-hander	A clock with three hands, typically the hour, minute, and seconds hands.
Three-quarter Plate	A large plate that covers the clockwork on the front (caseback-side) of the movement. The name comes from how it typically covers approximately three quarters of the movement, leaving room to expose the balance assembly for ease of regulation/adjustment. A three-quarter plate enhances the reliability of a movement by eliminating individual bridges which may be slightly misaligned during assembly and reassembly, shift due to shock or vibration, and cost more time to individually install. The massive plate also prevents lint and dust from entering the clockwork, a concern back when movements were frequently exposed to outside air by opening the cuvette. In the modern era of wristwatches with sealed casebacks and much finer manufacturing techniques, the three-quarter plate’s marginal utility is somewhat decreased. Nonetheless, it is regarded a signature feature of Saxon watches.
Throwaway/Disposable Watch	A watch meant to be discarded instead of repaired upon breakage. These watches were common as issued watches to infantrymen in the 1960s onwards when simple and reasonably accurate watches could be made for cheap.
Thunderbird	A nickname for the Rolex Oyster Perpetual Datejust Turn-O-Graph reference 6609 bearing the emblem of the United States Air Force Air Demonstration Squadron, also known as the Thunderbirds. It was not available to civilian buyers. ‘Thunderbird’ is a rare instance of an official nickname. It was an attempt by Rolex America to be associated with an American icon to capture the booming US market in the 1950s. However, in Rolex parlance, ‘Thunderbird’ refers to the entire ref.6609 range as well as its predecessor, the ref.6309 unlike the official designation which was limited to the emblazoned watches. The distinctive rotating bezel is thus dubbed the Thunderbird bezel.
Tiger	A nickname for the Tudor Prince Date chronographs of the 79200 series that have 'Tiger' written under the 30-minute totalizer at twelve o'clock. These watches were made in collaboration with American golfer Tiger Woods to promote Tudor's watches.
Time Ball	A time signal that consists of a large sphere mounted on a spire atop a highly visible structure such as a tower, turret, or skyscraper. The ball dropping down the length of the spire indicates a certain predetermined time, usually noon or 13:00. The raising of the ball to the top of the spire happens above five to ten minutes prior to the drop and indicates that timekeepers should be ready to adjust their timepieces. Before electrical methods of communication like the telegraph, time balls were mounted on buildings with highly accurate clocks that served as time standards, such as observatories. They were especially common in ports and harbors as vessels rely on time signals to synchronize their marine chronometers. While obsolete today, there are still several iconic time balls like the ones at the Royal Observatory, Greenwich and Times Square, New York City.
Time Signal	A visible, audible, mechanical, or electronic signal that announces the time from an accurate timepiece to another entity (a person or another timepiece). Time signals have been integral to human civilization since the beginning and their importance grows as our society becomes increasingly complex and interwoven. In the distant past, time signals were crucial in delivering time references for those without timepieces. After the proliferation of individual timekeeping devices they became time references to which clocks could be synchronized, which was particularly useful for transportation networks. In the current era, electronic time signals are indispensable in the operation of virtually all of our technology including computation, navigation, and communication. Some iconic time signals include church bells, time announcements, time balls, signal guns, telegraph time signals, and radio signals.
Time Standard	A specification for measuring time. There are numerous time standards used throughout the world to suit different purposes. Time standards usually rely on a specification for a rate at which time passes, the Earth's revolution and rotation around the Sun, or a combination of both.
Timekeeping Organ	An organ of a timepiece that is responsible for timekeeping. A timekeeping organ typically consists of a frequency reference, the structures that support the frequency reference, and some mechanism to relay the speed set by the frequency reference to the rest of the timepiece. As it is a loose term, it can refer to any group of parts or mechanisms that revolve around the aforementioned frequency reference.
Timepiece	A device that measures and/or indicates time. Synonymous with 'clock'.
Timex	A watch manufacturer established in Waterbury, USA in 1854 and now headquartered in Middlebury, USA. Timex is owned by the Timex Group.
Timezone	A geographical area which uses a uniform time standard for administrative, commercial, and social purposes. Every timezone is a positive or negative offset of UTC (Coordinated Universal Time), usually in one hour increments. Timezones are usually a compromise between geographical position (15 degrees of longitude for one hour offset) and political boundaries, with some exceptions like China, India, Greenland, and Central Europe.
Timing Complications	A family of complications that concern the measurement of elapsed time. The majority of timing complications are variants of the chronograph, which is a stopwatch. This includes the simple chronograph, the flyback chronograph, and the complicated rattrapante chronograph. Some non-chronograph timing complications include the deadbeat seconds and the flying seconds.
Tintin	A nickname for the Omega Speedmaster Professional reference 311.30.42.30.01.004. The nickname ‘Tintin’ is a reference to the Belgian comic series 'The Adventures of Tintin' where in volume 16 ‘Destination Moon’, the protagonist boards a moon-bound rocket with a red-and-white checkered fuselage. This checkering is reflected on the watch’s chapter ring.
Tissot	A watch manufacturer established in Le Locle, Switzerland in 1853. Tissot is owned by the Swatch Group.
Titanium (Ti)	An element used in the manufacture of watches. Titanium is lightweight, strong, corrosion-resistant, magnetism-resistant, and highly biocompatible. It is almost twice as light as most stainless steel alloys while being just as strong if not stronger. Its titanium oxide layer makes scratches more visible than stainless steel but it also makes it hypoallergenic. However, it is far more expensive to craft than stainless steel and cannot be polished to the same degree.
Tokei Zara	(Japanese?) A nickname for the Seiko 5 Sports Speed-Timer reference 6138-0020 automatic chronograph sporting a helmet case. The name is apparently supposed to mean 'bowl watch' as a reference to its case, but the name does not make grammatical sense and is likely a poor translation. Nonetheless, the name is the most widely accepted nickname in the Anglosphere. In Japan the watch is called 'Fujitsubo' (barnacle) due to its case. It shares this nickname with the watches the Anglosphere calls the 'Helmet'.
Tokyo Stripes	See 'striping'. Used to describe striping done on Japanese watches.
Tongue	The end of the long strap piece. Usually pointed or rounded for easier insertion through the buckle.
Tonneau Case	(French) Barrel. A case shape distinguished by a barrel-like profile resembling a tall rectangle with convex vertical sides, usually with narrow and flat horizontal sides. Sometimes confused with a style of cushion case. The cushion case in question has lugs integrated in the design and almost always a round bezel and dial that do not follow the case shape. A tonneau case almost always has a conforming bezel and dial shape.
Tool Watch	A watch whose primary purpose is to assist the wearer in a task, not to serve as an accessory or piece of jewelry. In watch collecting parlance the term primarily refers to watches designed for physical tasks such as combat, diving, mountaineering, flying, and racing. However, watches that perform mathematical calculations, measure pulse and respirations, or time events can all be called tool watches. The term is somewhat vague and ill-defined and may thus mean different things to different people. In many instances people refer to any durable watch as a tool watch.
Top Grain Leather	A layer of leather. Top grain leather refers to all leather types that are cut from the top half of the papillary portion, or grain portion, of the animal hide. It includes full grain leather, enhanced grain leather, and nubuck. Many erroneously use the term interchangeably with 'enhanced grain leather'.
Tough Solar	A brand of light-powered quartz movement produced by Casio G-SHOCK.
Tourbillon	A mechanism - sometimes described as a complication - which rotates the entire balance and escapement on at least one axis in order to negate positional errors and average out the influence of gravity on the timekeeping organ. This is achieved by mounting the balance and escapement in a rotating cage mounted on an axis or axes. 'Tourbillon' is French for 'whirlwind'. The tourbillon is a controversial mechanism in many ways as there is debate as to whether it can be considered a complication. Its efficacy is also often challenged as the mechanism was most useful for pocket watches which stay in one position most of the time, not for wristwatches which constantly move around anyway. Nonetheless the tourbillon is almost universally seen as an icon of high horology. It is often displayed through a dial cutout.
Tower Clock	See ‘turret clock’.
Train	Short for ‘wheel train’. Can also be short for 'going train'.
Transitional	In watch collecting parlance, a ‘transitional’ reference or component is one that sits between two different eras. Watches with transitional components such as transitional dials, movements, bezels, or cases may be at the tail end or beginning of a reference, or may be a standalone reference. In the latter case they are considered a transitional reference. Transitional references and components are important clues in understanding the history of watches, particularly in the context of a single manufacturer.
Travel Case	A form of watch storage designed for travel. Travel cases typically have hard shells, minimal in mass, and have tight cushions and padding to minimize watch movement when in transit. They always have some sort of fastening mechanism such as a zipper, latch, lever, or strap.
Travel Clock	A clock style of the 20th century designed to be used as a small deployable table clock on travels. The clock face is typically hidden in some case or beyond a cover until it is deployed. A travel clock usually comes with some sort of structure that allows it to be propped up on a surface such as a nightstand or desk. Travel clocks were useful in long train rides or in hotel rooms.
Travel Complications	A family of complications that concern the tracking of two or more timezones or assist in cross-timezone travel. This includes the common and adored GMT complication, dual time complication, and worldtimer complication.
Traveler GMT	A GMT that has an independently-adjustable hour hand. This configuration is useful to people who travel often and need to adjust the local time frequently, hence the name 'traveler' GMT. The traveler GMT configuration allows the wearer to adjust the hour hand in one hour increments while the movement is still running. Normally the GMT hand would be set to home time. Traveler GMTs are useful for professions like pilots, aircrew, sailors, and others who frequently move between timezones. Also see 'caller GMT'.
Tray	Also called a 'valet tray'. A portable receptacle with a flat surface usually lined with soft material that is used for the display or short distance transportation of watches. Trays provide protection from potentially abrasive surfaces, good color contrast for observing the watch, and a way of organizing small objects and tools on a desk surface. Trays are exceptionally useful for containing spring bars during strap changes as the walls prevent them from rolling away.
Tremblage	(French) A method of finishing where a burin is moved in a trembling motion to create a rough dimpled texture on metal.
Trench Watch	A subcategory of the field watch defined by its round case, wire lugs, and a protective shield for the crystal. These watches were among the first wristwatches on men's wrists and saw action in the European colonial wars and campaigns of the 19th century. They saw extensive use in the trenches of the First World War, hence the name. These watches had wire lugs which were soldered onto pocket watch and pendant watch cases to accommodate straps. They were fitted with high contrast dials (either black or white) with highly visible blocky Arabic numerals which were often lumed with radium. Some were fitted with metal shields called shrapnel guards that were skeletonized so that one could still read the time. While the watch fell out of use in the interwar period, trench watches are still popular among certain enthusiasts.
Triangular Case	A case shape distinguished by a triangular profile.
Triangular Tooth	A tooth cross section consisting of two symmetrical straight profiles. The straight profiles that make up a triangular tooth are rarely used compared to cycloid and involute profiles due to their inefficiency, but they have the advantage of meshing perfectly with each other. Moreover, the straight profiles allow for easy engagement and disengagement. This makes them ideal for chronographs.
Tribute	A watch that pays tribute to and reflects features of a previous reference, style of watch, historical event, etc. The term is broad, but in the narrowest sense refers to a watch that mirrors certain aspects of a preexisting reference (which may or may not be from the same manufacturer) but not closely enough to be considered an homage (if by a different manufacturer) or a reissue (if by the same manufacturer).
Triple Calendar	A simple calendar complication that displays three things: the date, day, and month. A watch that has a triple calendar complication may also have other calendar complications such as a moon phase complication. While this technically makes it a complete/full calendar, the watch may still be referred to as a triple calendar. The distinction between a triple and complete calendar is hazy and many use the two terms interchangeably. The triple calendar is sometimes confused with the perpetual calendar due to their visual similarities. The major difference is in the mechanics and the existence of a leap year indicator.
Triple Six	A nickname for the Rolex Oyster Perpetual Sea-Dweller reference 16660 due to the three consecutive sixes in its reference number.
Triple Split Chronograph	A variation of the split-seconds chronograph which is capable of splitting the hours and minutes as well as the seconds. Unlike the regular split-seconds chronograph which can only record the difference in two time intervals in seconds, the triple split chronograph has splitting chronograph hour and minute hands which records the elapsed hours and minutes of the split. As the hour is the largest unit of time measured by a chronograph, the triple split is often regarded as the final evolution of the split-seconds chronograph.
Triple-signed	Bearing three signatures on the dial. Almost never occurs. In another sense, a triple-signed pocket watch is one that bears the manufacturer signature in three places: the dial, movement, and case.
Tritium	A radioactive isotope of hydrogen used for lume. Also known as hydrogen-3, abbreviated 3H in chemistry and simply 'T' in watchmaking. Tritium is radioluminescent and thus self-luminescent - it emits light without the need for electricity or absorption of photons. When kept inside a tube, the beta decay of tritium releases electrons which interacts with a phosphor layer to emit a strong luminescence. While tritium is very bright and essentially always glows, its half-life of twelve years and continual phosphor degradation eventually dims its glow significantly. Unlike the similarly self-luminescent radium, tritium does not pose a health risk unless there is direct exposure or ingestion, in which cases it is still minimally dangerous. Tritium can be carcinogenic in extremely large quantities but the quantity found in wristwatches cannot even penetrate the skin.
Tritium Dial	A dial with tritium lume. The presence of tritium is usually marked with a T or two at the six o'clock marker or a roundel with a T in it somewhere on the dial.
Tropical Dial	A dial with discoloration as a result of defective paint reacting to intense sunlight over a long time. The exposure to ultraviolet radiation bakes the paint on the dial, resulting in bleaching. The most common color change is that of black to brown, with dark blue to magenta, white to cream, and black to blue also prevalent. As with most manufacturing defects packaged with romantic names, tropical dials are not universally liked. However, some tropical dials do age beautifully and command huge premiums over their better-preserved counterparts.
Trou Borgne	(French) See ‘blind hole’.
True GMT	See 'traveler GMT'. In common usage, 'true GMT' refers to a traveler GMT. It implies that a caller GMT is not a 'true' GMT as it lacks the independently adjustable hour hand that makes a traveler GMT suited for international travel. Traveler GMTs are also more mechanically complex than caller GMTs, which could be a reason for their prestige. In reality both caller and traveler GMTs are useful in their own ways.
Tudor	A watch manufacturer established in Geneva, Switzerland in 1926. Tudor is owned by the Hans Wilsdorf Foundation.
Tuna	A nickname for the various Seiko dive watches that follow in the pattern of reference 6159-7010, distinguished by its protective shroud which envelops the case flanks. The name comes from the shroud's resemblance to a tuna can.
Tuning Fork	An acoustic resonator in the shape of a two-pronged fork. In watchmaking, steel tuning forks briefly served as the timing reference for certain electric watches due to the constant frequency of its resonation once stimulated by electromagnets. Even after steel tuning fork electric watches were rendered obsolete by quartz crystal timing packages, tuning forks still technically serve as timing references as the quartz crystals are cut into tuning forks.
Turnip	In watchmaking, a 'turnip' is a recurring name for large and bulky watches. Pocket watches with the space-inefficient verge escapements were often called turnips due to their thickness. Turnip was also the nickname of Sir Winston Churchill's Breguet no. 765, a yellow gold pocket watch with a split-seconds chronograph and minute repeater ordered in 1890 by Churchill's paternal grandfather the 7th Duke of Marlborough. The exact etymology behind Churchill's Turnip is unknown.
Turret Clock	A clock style designed to be mounted on a turret or tower of a military fortification, religious or political building, or as a standalone structure as a clock and/or bell tower. Also known as a ‘tower clock’. Turret clocks were the standard public timepiece for centuries in Europe. They often also had bells or gongs to announce the time by sound.
Turtle	A nickname for the Seiko references 6306 and 6309 divers as well as the modern Seiko dive watches inspired by them (e.g. the SRP77X and SRPE07X series). Sometimes the name refers to earlier cushion-cased 6105 series divers. Technically this is incorrect as the true Turtles and the 6105s have vastly different case profiles. See 'Captain Willard'.
Tuxedo Dial	A dial configuration consisting of similar parts black and white (or similar colors like off-white or cream), typically in a bullseye configuration.
Twisted Lugs	A style of lugs (usually tapered) that are sculpted so that an accent line (the edge of two angled surfaces) runs from the outside of the lug at the base and ends at the inside of the lug at its tip. This is opposed to a normal lug where the outside line ends at the outside of the lug and inside line ends at the inside. The crossing accent line gives the appearance of a twisted lug. This style is also called ‘bombé lugs’ and ‘lyre lugs’.
Two-hander	A clock with two hands, typically the hour and minute hands. The two-hander wristwatch is often seen as the dressiest and most formal style due to its elegant simplicity.
Two-tone	Consisting of two colors. In a watch case or bracelet, two-tone usually refers to a combination of a yellow metal and white metal such as yellow gold and stainless steel. It generally does not refer to a combination of similarly colored metals such as white gold and stainless steel. On a dial, two-tone can refer to any combination of colors regardless of their similarity, such as white and off-white. The colors pertain to just the dial and not features such as markers or dial text.
Uemura	A nickname for the Seiko reference 6105-8110 diver and its various modern reissues. The watch was worn by Japanese explorer Uemura Naomi on his numerous conquests and expeditions around the world until he disappeared at Denali in 1984. In the West the watch is better known as the 'Captain Willard' after a fictional movie character. See 'Captain Willard'.
UFO	A nickname for the Seiko 6138-001X series automatic chronographs. The name comes from the watch's extra-round profile thanks to its hidden lugs and large round case. It is also known as the 'Yachtman'.
Ultraman	A nickname for the Omega Speedmaster Professional reference 145.012-67, a Speedmaster ref.145.012 fitted with an orange chronograph seconds hand. The reference 311.12.42.30.01.001 which was inspired by the ref.145.012-67 is also called the Ultraman. The name comes from the Japanese superhero Ultraman and the eponymous TV series, where the watch was prominently featured in episode 8 of The Return of Ultraman.
Undercut Profile	A profile has an undercut when the fillet curve lies concave inside a line connecting the end of the working profile and the root. Simply put an undercut is a round cut in the base of the tooth profile. Undercuts may remove interference in meshing. Undercut profiles are common in watchmaking.
Underline Dial	A nickname for tritium conversion Rolex dials of the early 60s (ca. 1963-1964) which feature a small horizontal line typically under the six o’clock dial text. Some are under the twelve o’clock text which earned them the nickname ‘upperline dial’. The underline dials are understood to be markings for internal reference, indicating a dial that was originally supposed to have radium but eventually painted with the newer tritium lume. Underline dials temporarily coexisted with newer, more official markings of tritium such as ‘Swiss - T < 25’ and ‘T Swiss T’ before being replaced by them. Also see ‘exclamation point dial’, ‘Swiss - T < 25’, and ‘T Swiss T’.
Unidirectional Rotational Bezel	A bezel which rotates in only one direction. A unidirectional rotating bezel is utilized almost exclusively in a diving bezel, where it is a safety feature. A typical count-up diving bezel only turns counterclockwise as in the event of a knock, brush, or scrape which moves the bezel, a unidirectional bezel will overstate the elapsed time underwater. This forces the diver to surface earlier than scheduled but is much more preferable to the contrary where the bezel understates elapsed time.
Uniform Timezone	Military timezone name for UTC+8.
Unique	In watchmaking and watch collecting parlance, 'unique' means that there is one and only one example in existence. It should not be conflated with the normal use of the word which carries the meaning of 'distinct', 'special', or 'creative'. Typically discussions around watches carefully avoid using the word in a potentially confusing manner. A unique watch or clock is called a 'pièce unique'.
Unisex Watch	A watch designed with both male and female wearers in mind. As women often wear 'men's watches', many men's watches are regarded as unisex.
Universal Genève	A watch manufacturer established in Le Locle, Switzerland in 1894. Abbreviated ‘UG’ and alternatively written ‘Universal Geneve’ without the accent. Universal Genève is owned by Breitling.
Universal/World Time Complication	A complication that simultaneously displays the time for all 24 major timezones on the planet. This is achieved through a rotating hours ring marked with the 24 hours of the day and a cities ring marked with one representative city for each of the 24 timezones. The corresponding hour to each city indicates the time of that timezone. Many watches with a universal time complication are embellished with a polar azimuthal projection of the globe at the center of the dial which may assist in visual clarity or decoration. Watches equipped with this complication are called 'worldtimers'.
Unworn	A timepiece is considered unworn if it has never been worn. Verifying this is virtually impossible, so 'unworn' is sometimes treated as a catchier synonym for 'mint'. Watches that still remain in their original packaging may be described as unworn. It is obviously required that a timepiece declared to be unworn be mint.
Upperline Dial	See ‘underline dial’.
Urwerk	A watch manufacturer established in Geneva, Switzerland in 1995. Urwerk is privately owned.
UT1	Universal Time. UT1 is a time standard based on the Earth's rotation, and technically a solar time. The '1' is used to distinguish the most conventionally used form of Universal Time
UTC	Coordinated Universal Time. The acronym 'UTC' is a compromise between the English 'Coordinated Universal Time' (CUT) and French 'Temps universel coordonné' (TUC). UTC is a time standard (not a timezone like GMT) and is not a solar time (unlike UT1). It is effectively a more accurate successor to Greenwich Mean Time (GMT) that requires fewer adjustments than the daily corrections need by GMT. UTC is also a compromise between the mean solar time that is UT1 (Universal Time) and the atomic time that is TAI (International Atomic Time) - UTC relies on atomic clocks like TAI, but adds leap seconds in order to keep up with the more commonly used UT1 solar time. In common, casual use by laymen, UTC is equivalent to UT1 and GMT. Also see 'UT1', 'TAI', and 'GMT'.
UTC Complication	See 'GMT complication'.
UTC Hand	See 'GMT hand'.
Vacheron Constantin	A watch manufacturer established in Geneva, Switzerland in 1755. Abbreviated ‘VC’. Vacheron Constantin is owned by Richemont.
Valet Tray	See ‘tray’.
Velcro Strap	A strap fastened with velcro or similar hook-and-loop fasteners. Velcro straps are almost always one-piece fabric and follow the style of nato or zulu straps for the looping while using velcro to tidy the remaining length of the strap. Compared to their almost identical nato and zulu counterparts, velcro straps have the advantage of securely adhering the remaining strap length flush to the wrist. The former two often become looser or slip out of their loops when there is not enough tension on the strap length, or when the strap snags or brushes against another surface. Velcro is also a great way to tidy lengthy straps which is why they are used for astronaut straps which go over spacesuits. However, velcro tends to attract dust, sand, and lint and can be difficult to clean. It may also adhere to woven fabric on the wearer's sleeve.
Verge Escapement	An escapement that utilizes a crown wheel and a rod called a 'verge' to engage the oscillator and train. Also called a 'crown wheel escapement'. It was the first mechanical escapement in history, mechanizing the regulating organ of a clock that still relied on non-mechanical forces such as the flow of liquid. Thus the verge escapement birthed the all-mechanical timepiece and set the precedent for the oscillating timekeeper such as pendulums and balance wheels. In the system's various iterations, the common principle is that a crown escape wheel axised horizontally to the ground is locked and unlocked by a vertical verge with two offset pallets. The oscillation of the rod on its axis shifts the positions of the pallets so they lock the escape wheel teeth one at a time. In its incipiency the escapement utilized an oscillator called a foliot which was a yoke with a weight on each arm that was mounted to the top of the verge. The foliot was later replaced by the pendulum and balance wheel.
Verge Reconversion	A restoration of a watch that had its original verge escapement switched out to the newer anchor escapement.
Vertical Clutch	A chronograph clutch system that is arranged vertically in a single column and integrated with the main wheel train. As per its arrangement, a vertical clutch engages and disengages vertically by friction coupling instead of meshing gears, like the clutch in an automobile. A vertical clutch is by nature always meshed, and thus have tighter tolerances. This allows a movement with a vertical clutch to operate more smoothly, which means that long-term wear is minimized (also due to the lack of meshing) and the seconds hand does not wobble when started. Vertical clutches do not affect the amplitude of the main movement unlike a lateral clutch.
Vianney Halter	A watch manufacturer established in Sainte-Croix, Switzerland in 1998. Vianney Halter is privately owned.
Vibration	An action of the timekeeping organ. A vibration can either be a single semi-oscillation of a balance spring in a mechanical movement - in which case it is more commonly called a ‘beat’ - or a vibration of a quartz oscillator or metal tuning fork in reaction to electricity in a quartz or electric movement. Vibrations over a certain period of time can be a measurement of frequency and uses the unit vibrations per hour (vph) in mechanical movements. In quartz movements, the extremely high rate of vibrations brings the common unit down to vibrations per second (vps).
Vice	A tool that fastens a component such as a bracelet in place.
Victor Timezone	Military timezone name for UTC+9.
Vintage	In watchmaking, 'vintage' generally refers to an object that is over thirty years old. There is no exact definition, with some putting the line at twenty and others at thirty-five.
Vitreous Enamel	A type of enamel that fires powdered, usually colored, glass at high temperatures until it becomes a glassy substance that fuses with an underlying surface (substrate), usually porcelain or metal. It is a useful technique for decoration and is commonly used in the more artistic realms of watchmaking.
Vomit	A mostly pejorative nickname for the Rolex Oyster Perpetual Submariner 16610LV more popularly known as the ‘Kermit’. The olive green bezel was received with mixed reactions, and those who were put off by the color called it the ‘Vomit Sub’. The nickname has since become far less common.
Vph	Vibrations per hour. A unit of measurement for frequency. Vph can be used for any movement type but is commonly used for mechanical movements.
W.I.S./WIS	Watch Idiot Savant. WIS is a sarcastic term for a person who is obsessed with wrist watches, especially the technical details, reference numbers, and niche facts. The term is usually used in a humorous self-deprecating manner.
Wadokei	(Japanese) A mechanical clock that tells traditional Japanese time. The clocks existed from the 17th century when the first Japanese clocks were made based on mechanical timepieces brought by Europeans until the 19th century when the Meiji Restoration saw the abolishment of traditional Japanese time in favor of European standards of timekeeping.
Wako Edition	A special edition Seiko made for and sold in Wako department store, a luxury retailer owned by the Seiko group. Wako special editions are typically limited editions of Grand Seiko or Credor models. A popular theme is the introduction of numerals to watches that normally have baton indices. Breguet numerals seem to be the most common addition in Wako edition watches.
Wall Clock	A clock style designed to be hung on a wall. Wall clocks came in many forms before the advent of quartz movements which allowed the clocks to be simple and thin. These include lantern clocks which served as wall clocks in Europe for around three centuries.
Wally Schirra	A nickname for the Omega Speedmaster reference 2998, named after American astronaut Walter Schirra who wore it during the 1962 Sigma 7 mission. This mission was the first time an Omega watch was ever worn in space, giving the ref.2998 another nickname - the First Omega in Space, or ‘FOIS’. Unlike FOIS which refers to all Speedmasters inspired by the ref.2998, ‘Wally Schirra’ refers to only the ref.2998.
Watch	A portable timepiece/clock designed to be carried or worn by a person. Popular types of watch includes the 'wristwatch' which is worn on the wrist and the 'pocket watch' which is kept in a pocket.
Watch Box	A form of watch storage and display that utilizes a wood, resin, plastic, leather, or metal box with an openable cover/lid. Watch boxes keep watches safe but are meant to be stationary. Many have glass covers to display the watches even when the box is closed.
Watch Case	A form of watch storage that utilizes a hard external shell and a padded interior to keep a watch safe, usually in transit. Cases come in many forms and is more of a generic term for the various protective cases available.
Watch Conglomerate/Group	A large corporation that has more than one watch brand as a subsidiary. Watch conglomerates arose in the 1980s and 1990s as companies started to sweep up the remains of the decimated mechanical watchmaking landscape left in the wake of the Quartz Crisis. Today most of the biggest brands are part of a watch conglomerate with some big players including the Swatch Group, Richemont Group, Moët Hennessy Louis Vuitton, Seiko Group, Citizen Group, and the Kering Group.
Watch Over Cuff	The act of wearing a wristwatch over the cuff of an article of clothing. Also called 'over the cuff'.
Watch Pouch	A form of watch storage that utilizes a small and portable pouch made of leather or fabric.
Watch Roll	A form of watch storage that utilizes a rectangular piece of fabric lined with a softer fabric and sewn with individual pouches for watches. The fabric is rolled into a cylinder and wrapped with a cord or rope of some kind. The lining is usually thick and supple to prevent damage when the roll is rolled up.
Watch Snob	A person who looks down on certain watches based on brand, price range, or country of origin. What constitutes a watch snob is subjective. While the term is pejorative and often used to describe unpleasant individuals with snobbish opinions on affordable timepieces, it is sometimes reclaimed by watch enthusiasts who categorically dislike poorly-made and overpriced timepieces regardless of price category or maker.
Watch Tan	A tan mark that results from wearing a wristwatch often. In many cases the watch tan serves as a mark of honor in the watch community.
Watch Trunk	A form of watch storage designed to carry a large number of watches and accessories in style. Watch trunks come in many styles but they typically come in the form of a large lockable briefcase with numerous slots for watch cushions. They almost always come with a carry handle.
Watch Winder	A device used to wind a watch. With a few exceptions, watch winders are built to keep automatic watches constantly wound so that they are immediately usable. They usually come in the form of a box with a removable watch cushion mounted on an electrically powered rotating surface. Fastening the watch onto the cushion and powering up the winder keeps the watch wound without the owner's having to wear it. There are winders for certain manual wind mechanical watches as well, although they are exceedingly rare. These are usually proprietary winders that come with special models, usually with absurdly long power reserves.
Watchmaker	An individual or entity that is involved in the creation and/or maintenance of timepieces.
Watchmaker's Four	A variation of the Roman numeral for the number four where the numeral is written as [IIII] instead of as the more common version [IV]. There is no clear origin as to how it came to be. It is commonly understood to simply be an aesthetic choice. While not all dials feature the watchmaker's four, it does seem to be far more common than the conventional Roman four.
Watchmaker’s Screwdriver	A type of screwdriver with a short shaft and a flared rotating butt that allows the watchmaker to brace the screwdriver with the index finger while turning the driver with the thumb and middle finger. Watchmaker’s screwdrivers are ideal for the small screws that are in watch movements.
Watchmaking	The craft/art of manufacturing timepieces. While synonymous with ‘clockmaking’, the dominating prevalence of watches in today’s world has made ‘watchmaking’ a far more common generic term.
Water Clock	A timepiece that utilizes the constant and regulated flow of water to measure time.
Water Resistance	A timepiece's ability to stop water from entering the case. Water resistance is measured in the units of water pressure which also corresponds to depth. Common units include meters (m), feet (ft), standard atmospheres (atm), and bars (bar). Water resistance is usually achieved with a watertight case with special gaskets and threaded parts.
Water Resistant	In watchmaking, 'water resistant' is a designation given to watches that are capable of keeping water out of the case. It is usually accompanied by a precise numerical rating (in meters, atmospheres, bar, or feet) to specify the maximum amount of water pressure the case can withstand. Watch manufacturers must abide by standards set by the relevant standards organizations such as ISO to mark their products as water resistant. Water resistant ratings can be misleading as the maximum water pressure a watch can withstand in a highly controlled test environment is not necessarily the maximum depth at which it will work in a pool or lake. For example, a 30m depth rating means that the watch is suitable for rainfall but not much more. However, dive watch depth ratings are done on a different scale. In addition to far more tests, every dive watch is tested to at least 125% of its declared rating. Hence, a watch that meets diver standards will easily operate at the stated maximum depth.
Waterproof	In watchmaking, 'waterproof' was a designation given to water resistant watches before the adoption of industry standards on water resistance. This period roughly extends from around the mid-19th century to the 1980s. From the end of WWII to the 1990s, precise depth ratings started to accompany 'waterproof' designations. From the 90s onwards, 'waterproof' has been totally erased from watch performance ratings. This is because it is technically impossible for a watch to be waterproof in the plainest sense of the word. Several international standards organizations outright ban the use of the term, including the influential ISO 2281 standard for water resistant watches introduced in 1990. Today, 'waterproof' is not taken as any serious indication of water resistance and instead indicates that the watch is likely old and that it may incorporate certain design features such as a screw-down crown and caseback, and pump pushers.
Welded Lugs	Lugs which have a clear and visible welding line between the base of the lug and case, or any lugs that are attached through welding regardless of visibility. Welding is a metal-joining technique that fuses two metal pieces together by melting them at a high temperature. In the watch world, welding is not a common technique as it melts the workpieces instead of using a filler metal that melts at a lower temperature than the work pieces as an adhesive. The results of welding are typically not acceptable in casemaking standards. Welding as a technique is sometimes seen in DIY/garage jobs for fixing bars to lugs.
Wellendorff	A jewelry manufacturer established in Pforzheim, Germany in 1893. They are renowned for creating the bracelets for Saxonian watchmaker A. Lange & Söhne from 1994 until the late 2000s.
Wellendorff Bracelet	A bracelet manufactured for A. Lange & Söhne. In the company's early days following its rebirth, most models had a bracelet option. Lange's partnership with Wellendorff ended some time in the late 2000s.
Western Arabic Numerals	See 'Arabic numerals'.
Westminster Chime/Quarters	A renowned chime that marks the quarters. The Westminster chime is famously played by the bells of Elizabeth Tower at the Palace of Westminster. Each quarter plays a different combination of one or more out of five total changes (one change consisting of four notes). The chime gets longer with each quarter until the full hour chime, when four of the five changes are played and succeeded by the appropriate number of strikes of Big Ben, the hour bell. Smaller striking timepieces may put a slight variation on how the hours are chimed as it is more common for the hours to be chimed first, if the quarters are chimed at all at the full hour.
Wheel	A large gear. A wheel usually has anything between 20 to 80 teeth. Also see 'pinion'.
Wheel Train	The wheel train of a movement refers to the gear train, which is a system of gears that delivers energy from the mainspring to the watch to the balance, rotates the hands of the watch, and performs auxiliary functions. Trains consist of a combination of large gears called ‘wheels’ and small gears called ‘pinions’ mounted on axles called ‘arbors’. While watches and clocks may have quite different trains, there are largely three trains within every movement: the ‘going train’ which transmits energy, the ‘motion work’ which turns the hands via a reduction train, and the ‘keyless works’ which performs functions like winding the mainspring and setting the time.
Whip Hands	A style of hands distinguished by a leaf-style curved body with a diamond tip. Whip hands are typically not lumed.
Whiplash Regulator	See 'swan neck regulator'.
Whirlpool	A nickname for the Grand Seiko reference SBGH267, a watch sporting a radially tessellated dial with alternating Gs, Ss, and Daini Seikosha lightning logos. The nickname comes from the whirlpool-like pattern on the dial.
Whisky Timezone	Military timezone name for UTC+10.
White Gold	An alloy used in the manufacture of watches. Abbreviated Wg. White gold is an alloy made of pure gold (Au) and at least one type of naturally white metal such as nickel, silver, palladium, and platinum. White gold is often but not always plated with a thin rhodium layer to make it appear whiter. White gold is not to be confused with platinum (Pt), which is an entirely different metal and an element of its own. As a gold alloy, white gold has its purity measured in carats. Naturally, white gold cannot be 24 carats (24k) as there is no way that an alloy with 99.9% purity in a naturally yellow metal like gold can be even remotely white.
Wide Boy	A nickname for dials on the Rolex Datejust references 1601/3, and Day-Date reference 1803 with wider-than-standard indices.
Willard	See 'Captain Willard'.
Winding Pinion	A pinion that engages the keyless works to wind the mainspring.
Winding Stem	See ‘crown stem’.
Window	A cutout in the dial which reveals what is underneath. Synonymous with 'aperture', although windows usually refer to an aperture that displays some sort of information as opposed to a part of a movement. Generally the terms are interchangeable.
Wire Lug	A style of lug that is essentially a shaped wire loop attached to the case. Wire lugs are a simple way to accommodate straps and were particularly popular when wristwatches were still just converted pocket and pendant watches. Some modern designs still use wire lugs for aesthetic reasons. Functionally it is no different from the fixed bar.
Wire Lugs	A style of lugs distinguished by a single wire bent in a bracket shape ( [ ) to replace a pair of lugs. Wire lugs were among the first lugs on wristwatches and started out as wires soldered onto pocket and pendant watch cases to accommodate straps. Wire lugs can only accept either one-piece straps or antiquated leather straps that have loops.
Wolf-tooth Gear	A gear with asymmetrically-profiled teeth which slope in one direction and peak at a slightly curved tip in a way that resembles a beast's fang. Wolf-tooth gears are generally regarded to be more stylish versions of the more common saw-tooth gear.
Women's Watch	A watch designed with a female wearer in mind. Modern women's watches typically range from 30mm to 40mm in case diameter.
Wood Dial	A dial made of wood. While not a common choice for dials due to its proneness to cracking, splitting, and decay, wood can be a desirable material if treated correctly. Wood dials are typically crafted out of burl wood, which is a section of the trunk with deformed unsprouted bud tissue. Burl wood yields beautiful burl grain which is highly desired in woodworking. Common woods used for dials include mahogany, madrone, birch, and walnut. The wood dials are typically treated with a strong lacquer coating to prevent the usual issues that plague untreated wood. The resulting product can resemble a dial made of gemstone.
Worldtimer	A watch equipped with a universal/world time complication.
WOTD	Watch collecting social media lingo meaning 'Watch Of The Day'. Usually accompanied by a wrist shot of the chosen watch of the day.
Wrist Check	Watch collecting social media lingo for a ‘check’ of what watch is on the wrist. Usually accompanied by a wrist shot.
Wrist Cheese	A colloquial term for the accumulations of dead skin, bodily fluids such as sweat, perfumes and lotions, and other miscellaneous items that form under a wristwatch. Wrist cheese is often unsightly and pungent, especially in watches with leather or fabric straps. They are also found in the crevices and joints of watch heads and bracelets. Removing wrist cheese is straightforward for water resistant watches, especially divers that can be blasted with pressurized water. There are also many products in the market to combat wrist cheese more delicately.
Wrist Roll	Watch collecting social media lingo for a video where the wearer rolls their wrist to show a wristwatch from clasp/buckle to head as well as how the watch’s surfaces reflect light.
Wrist Shot	A picture of a wristwatch on the wrist.
Wrist Time	The amount of time a watch gets worn.
Wristlet	An antiquated term for a wristwatch. As a diminutive word, it was sometimes used pejoratively. The word fell out of use in favor of 'wristwatch' within the first half of the 20th century. The term also refers to the equally antiquated wristlet strap. See 'wristlet (strap)'.
Wristlet/Converter (strap)	A style of one-piece strap, usually leather, which allows one to mount a pocket watch on the wrist. The strap is constructed of a cup-shaped leather receptacle sewn onto a heavy duty pin buckle strap. This style was popularized in the 19th century by men on bikes, horses, and automobiles who preferred to have the time readily available when their hands were occupied with steering. Wristlets were extensively used in European colonial campaigns until they were gradually replaced by watches with soldered-on wire lugs (which greatly reduced the bulk of the strap) in the First World War and purpose-built wristwatches in the interwar period.
Wristwatch	A watch designed to be worn on the wrist. Wristwatches are fastened to the wrist with some sort of band.
WRUW	Watch collecting social media lingo meaning 'What Are You Wearing'. Usually accompanied by a wrist shot of what the original poster is wearing.
X (reference number)	In reference numbering convention, 'X' stands for a variable digit. It is sometimes not capitalized. It is most commonly used to represent a family of related references that have mostly identical reference numbers. For example, Seiko references 6306 and 6309 are almost the same watch and have almost the same reference. Thus 630X can be a neutral name for the two watches, useful when talking about common features. When there are only two, a slash is sometimes preferred, e.g. 6306/9. See '/ (reference number)'. The mystery digit X should not be confused with the letter X sometimes used in alphanumerical references, e.g. Grand Seiko ref.SBGX26X where the first X is an alphabetical designation while the second X is the mystery digit. Distinguishing the two is a matter of intuition and familiarity with a particular company's numbering system.
X-ray Timezone	Military timezone name for UTC+11.
Yachtman	A nickname for the Seiko 6138-001X series automatic chronographs. The name comes from a Seiko advertisement which referred to the watch as the 'Yachtman's chronograph'. It is more popularly known as the 'UFO'.
Yankee Timezone	Military timezone name for UTC+12.
Yellow Gold	An alloy used in the manufacture of watches. Abbreviated Yg. Yellow gold is the closest in color to pure gold out of the colored golds and the two are often confused. As gold is too soft for most applications, it is alloyed with the red metal copper. White metals such as silver, nickel, or palladium may be added to make a creamier and lighter color as pure gold can look like brass.
Yoke	A lever that resembles a yoke (or half of a yoke). Yokes are almost universally used in the keyless works as a part of the setting mechanism. In this instance, the yoke is used to push the sliding pinion down the winding stem so that it can engage with the intermediate wheel to connect the crown assembly with the motion work.
Yoke Spring	A flat spring that applies pressure to the yoke, especially in the keyless works.
Zaratsu	(Japanese) A method of finishing and type of polishing proprietary to Seiko, Citizen, Minase, and some other Japanese manufacturers. The name is a Japanese transliteration of the German word 'Sallaz', the manufacturer of the polishing machines at the Seiko factories of old. Zaratsu (as Seiko brands it) and Sallaz (as Citizen, Minase, and Orient brand it) are broad terms and refer to a wide range of polishing levels. Higher end Zaratsu finishing is considered on par with, or a type of black polish. Also see 'Sallaz'.
Zenith	A watch manufacturer established in Le Locle, Switzerland in 1865. Zenith is owned by LVMH Moët Hennessy Louis Vuitton.
Zenith Daytona	A nickname for the 165XX series Rolex Oyster Perpetual Cosmograph Daytona, which uses a heavily modified El Primero automatic chronograph movement originally manufactured by Zenith. The watch was Rolex’s first Daytona in the Oyster Perpetual family as it was the first to feature an automatic movement.
Zero Reset Seconds	A complication that automatically returns the seconds hand to zero and hacks (stops) it upon pulling the crown to the time setting position. Whereas most watches require the wearer to wait for the seconds hand to return to zero to set the watch accurately, the zero reset seconds spares the wearer this waiting time.
Zulu Strap	A style of one-piece strap that is constructed using one piece. It is usually made of a fabric like nylon. The zulu strap is a simpler style than the similar and older nato strap as it uses only one piece to thread through the lugs and fasten to the wrist. The remaining strap length is tucked and organized with two articulating hoops. Like all other one-piece straps, its construction effectively fastens the watch not to the wrist but to the strap itself. If a spring bar fails due to high impact or abrasion, the watch head will dangle from the strap instead of coming off the wrist like it would with a two-piece strap. Zulu straps wear slightly differently from nato straps as it puts one, not two layers of fabric between the caseback and wrist. Choice between the two is usually a matter of preference. Also see 'nato strap', 'nato zulu strap', and 'RAF strap'.
Zulu Timezone	Military timezone name for Coordinated Universal Time (UTC). Also commonly called ‘Zulu time’.

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