Wrist Watch Lexicon

Annual Calendar

An annual calendar watch features a calendar function (see below) which displays the day, date and the month as well as time, the annual calendar must be set on the first day of March every year as it does not adjust for the 28 or 29 days in February. First patented by Patek Philippe in 1996.

Automatic Watch

An automatic watch requires no battery. The watch mainspring is wound automatically by an imbalanced wheel which is rotated by normal wrist motion whilst wearing the watch.


This is the ring around the case which holds the crystal of a watch to the case of the watch.

Bi-Directional Rotating Bezel

A bezel that can be rotated either clockwise or anticlockwise, usually accompanied by a GMT function.


The traditional loop and pin system on a watch strap is called a ‘buckle’.

Butterfly Clasp

An elegant type of clasp used on some high-end watches which features two small folding clasps as opposed to one large clasp.


A feature that shows the date, and often the day of the week and month. Most calendar watches show the information either digitally through an aperture on the watch face or through a sub-dial.


A word used to address the mechanism inside a watch.


A rare complication created by Danish inventor Bahne Bonniksen when he was working in England. The Carrousel is much like a tourbillon (see below), however, a carrousel uses a separate gear to drive the cage rotating around the escapement whereas a tourbillon uses one gear to power the escapement itself and the cage around it. Like the tourbillon, there is great debate over the effect it has on accuracy in modern wristwatches. It’s a technical complication that is most often used by Blancpain.


A case of a watch is the housing for the internal watch movement, water resistance and anti-magnetism are examples of watch features governed by the design of the case.

Case back

The reverse of the watch case that can be opened for access to the watch movement for repair or battery change. Some watches have a sapphire glass backing which allows you to see the working mechanism of the watch.


This is a watch with a stopwatch mechanism connected to the movement and is normally indicated via sub-dials. This can include hours, minutes, seconds or even days.


This is a watch which has been measured for accuracy and tested for precision by an official testing institute.

Complete Calendar (Quantième Complet)

A complete calendar is a type of calendar system which displays the date, day of the week and month as well as the phase of the moon. Unlike an annual or perpetual calendar, a complete calendar does not adjust for the days in a month, therefore the watch must be adjusted at the end of every month which does not have 31 days.


An additional function other than basic timekeeping of the hours, minutes, and seconds. Certain features such as automatic winding or date are considered complications. The most popular complications are power reserve indicator, moon phase, GMT, and calendars. Rarer complications include split second chronographs, perpetual calendars, tourbillons, and minute repeaters.

COSC (Contrôle Officiel Suisse des Chronomètres)

This is the Swiss Official Chronometer Testing Institute that will certify the official chronometer status of a watch, certain manufacturers are looking to use a more stringent test to verify accuracy in the future.


The crown is known better as the adjustment dial on the side of a watch. The crown is used to adjust the time, date and for winding up the watch, certain watches feature innovative crown features such as an inward moving crown (to protect the stem of the crown).

Crown Guards (Shoulders)

This is when the case is shaped so that the crown is protected from being knocked, most common on sports watches.


The crystal is the transparent cover over the dial. The most popular crystal currently is a sapphire crystal due to its resistance to scratches, however, resin crystals such as plexiglass were very popular with older watches.

Date Window

A small opening in the dial through which the date is displayed.

Deployment Buckle

The deployment buckle is a clasp that folds nicely into the strap as a more elegant solution.


The dial is the face of the watch showing the time indexes.

Diving Watch

A watch that is at least 200M water resistant. A diving watch has one way rotating bezel and a screw-on crown and back. Some watches have a helium escape button to release the pressure after saturation diving.


Set of parts (escape wheel, lever, roller) which converts the rotary motion of the train into to-and-fro motion (the balance).

End of Battery Life Indicator (EOL)

The EOL indicates when it is time to replace the existing battery. Different manufacturers use different methods to indicate a low battery, i.e. if a second hand usually sweeps, when the battery is low it will begin to tick or a ticking watch might tick in five-second increments instead.


This is how a watch will look once all manufacturing and testing are completed. The finishing of watches come in three types, a polished surface, a brushed finish and a plated finish.

Fly-Back Chronograph

This is a type of chronograph that is designed so that it can be reset while the chronograph is still running.

Geneva Stripes

A form of decoration in higher grade watch movements which look like uniform stripes.

Grand Complication

A Grand Complication is a combination of complications in one watch, usually featuring a perpetual calendar (with or without moonphase indication), a split-second flyback chronograph and a minute repeater. Manufactures quite often include many other complications as well.

Gregorian Calendar

The calendar system we currently use.


The subject of timekeeping.


In watch making, a synthetic ruby used for making low friction bearing in which the delicate pivots of the movement wheels run in. In some luxury watches, sometimes sapphires or garnets are used. Expensive watch movements are jewelled from the barrel to the balance, and all automatic work, date and complication movements are expected to be jewelled.


These are the points on the case which allow a strap or bracelet to be attached.


The hour markers and/or hands have a feature coating of a glow in the dark which will illuminates in the dark so you can tell the time where there is insufficient light. some manufactures use small tubes of glowing gas which can last for years without needing a change.


A French term for a watch factory which itself produces the components needed for the manufacture of watches.

Manual Wind

A watch which has mechanical moving parts and requires its mainspring to be manually wound through a mechanism.

METAS (Swiss Federal Institute of Metrology)

This is a recent development in the testing of a watch movement. METAS chronometer requirements are stricter than those of COSC which are now considered relatively easy to meet.


On some watches, the display of the evolution of the lunar cycle: rising, full or waning moon.


This is the internal mechanism of a watch. Assembly of parts and main components such as the mainspring, balance assembly, escapement, train of wheels, setting and winding.

Perpetual Calendar

A complication or function of a watch which displays correctly without adjustment, the day, date and month, and can also account for leap year cycles.

Power Reserve Indicator

A power reserve indicator shows the power resource of a mechanical movement watch.

PVD (Physical Vapour Deposition)

A method of coating watch cases by integrating titanium particles and then depositing gold for colour. (Usually comes in black finish)


This is a watch with a battery-powered mechanism as opposed to relying on a barrel and spring system.

Rattrapante (double chronograph)

A watch with a double chronograph has two seconds hands. One hand is superimposed over the other. While one hand moves continuously, the other one can be stopped, started or reset to zero in order to estimate two separate events of different durations.


A repeater is a complication in a mechanical watch or clock that audibly chimes the hours and often minutes at the press of a button. There are many types of a repeater, from the simple repeater which merely strikes the number of hours, to the minute repeater which chimes the time down to the minute, using separate tones for hours, quarter hours, and minutes. Often regarded as the most difficult complication to put in a watch or clock.


This is a hand on a watch dial which returns to zero at the end of a prescribed period i.e. seconds, minutes, days or months. For example, a watch may have a retrograde date, meaning that the hand moves up a scale one day at a time, pointing to the current date when it reaches 31 it will spring back to 1.


In automatic winding mechanisms, an unbalanced, semicircular piece of metal turns freely in both directions winding the mainspring.

Skeleton Movement

Movement on a watch where the plates have been removed or trimmed so that you can see the gears and other parts.

Skeleton Dial

This is when all but the essential parts of the dial have been removed so the wearer can see the movement without needing a sapphire caseback.

Water Resistant

Describes a watch case designed to prevent water from entering.

Tachymeter (Tachymètre)

A watch featuring a chronograph and a tachymeter bezel can be used for the measurement of speed. It measures speed in kilometres per hour based on 1000m distance.


This type balance is a complex piece of micro-engineering which results in the escapement of a watch rotating on its own axis; the aim is to negate the variations in running regularity which can be caused by gravity due to the watch being in different positions (a watch may gain time in one position yet lose in another).

Water Resistance Guide


A watch rated as water resistant may come in contact with water to a predetermined extent. Most watches have a measurement until which the depth of immersion is safe. It is important to remember that a water-resistance rating is based upon optimum conditions in a laboratory. Real life experience & ageing of the gaskets will effectively decrease the manufacturer’s specifications of water resistance over time. The worst scenario possible is that moisture is allowed to make contact with the movement – thus we strongly suggest that you always work well within the parameters of the manufacturer’s recommendations and have your watch tested at least once a year. Any competent watchmaker has the necessary equipment to test water resistance. It is important to remember that all watches have limits and no watches are waterproof.

Optimum water resistance on a watch is obtained by 3 important factors:

  1. Case back – this refers to how the case back is attached to the watch.

Snap-on case backs are sealed by pressure and are considered the least water resistant. The slightest nick in the case or a deformity in a gasket (which will happen over time) will allow water to penetrate the case. Generally, these watches will have a water resistance of 30m/99ft maximum – which allows for contact with water, such as washing hands, but not immersion.

Case-backs attached with screws are the second level of water resistance. Having the case back attached with screws allows for a much tighter seal than a snap-on case back, however a deformity in the gasket will still allow water to penetrate. Generally, these watches will have a water resistance of 100m/330ft maximum – which allows for light immersion such as swimming in a pool.

Screw-down case backs are threaded and screws into the actual case. This creates a double seal, using both the threading & the gasket as a seal coupled with the deep water pressure . Generally, diving watches with water resistant ratings greater than 100m/330ft will have this type of case back.

  1. Crown – the single most important factor to ensuring water resistance.

The weakest link in a watch for water to penetrate is the crown-stem hole. The stem of the crown is attached to the movement through a hole in the case edge. As the crown is constantly moved to different positions, wound and turned to correct the time, the gasket is constantly compressed, chafed & stressed. The slightest variation in the shape of the gasket or if the crown is not pushed all the way in will allow water to penetrate the watch through the stem hole.

Screw-Down crowns are threaded & screwed shut to a matching threaded tube in the case. The crown has a gasket that is compressed & seals the opening when the crown is tightened – thus ensuring water resistance. A screw-down crown is an essential feature for any watch you intend on swimming with. As matter of fact, we do not recommend swimming with a watch that does not have a screw-down crown. No matter if the watch has a screw-down crown & chronograph pushers, the crowns & pushers are never to be pushed, adjusted or operated when the watch is immersed in water – unless otherwise stated by the manufacturer. An additional benefit of the screw-down crown is that the crown is somewhat more protected from accidental knocks.

  1. Gaskets:

“O” rings are made of rubber, nylon or Teflon which form watertight seals at the joints where the crystal, case back and crown meet the watch case. If the watch is a chronograph, the chronograph pushers will also have gaskets to protect from dust and dirt, check with your manufacturer if you are unsure as to whether the pushers on your watch can be operated in wet conditions, it’s not a law that chronographs must be operable under water.

Gaskets begin to erode and break down over time, diminishing the water resistance of a watch. It is important to test you watch once a year for water resistance. Any competent watch maker should have the necessary basic equipment to test the watch – the cost involved should be minimal.

Real Life and Water Resistance

When a watch is tested by the manufacturer it is usually done in a laboratory under optimum conditions, such as a fresh gasket, sitting stationary in a pressured water tank and with still/motionless water. However, real life action will produce completely different results. Here are a few scenarios:

Water temperatures in a hot-tub or a hot shower will effect the shape of the gasket seals. Especially if the watch is taken from hot temperatures & immediately plunged into cold water – such as going from a hot-tub into a pool.

Sudden & rapid changes in pressure – such as diving (even shallow diving) into a pool, the force of plunging your arm into the water while swimming, will stress the gaskets for a fraction of a second. If the gaskets are not up to specification they may rupture and cause the watch to take in water.

As the watch ages the seals begin to erode & will not maintain the same water resistance levels.

Water Resistance vs. Water Proof

The U.S. FTC (Federal Trade Commission) which enforces the truth-of-advertising has deemed the term “Waterproof” inappropriate. In their opinion, a watch can never be 100% truly impervious to water, as the gaskets deteriorate over time & exposure, thus reducing the specified depth of water resistance. In the words of the FTC: “The word proof connotes a measure of absolute protection that unfortunately does not exist with respect to watches, especially over prolonged periods of time.” The FTC has found the term Water Resistant to be more appropriate.

Water Resistance Testing Methods

There are 2 commonly used water-resistance testing methods:

Dry Test – The watch is placed in a chamber and the air-pressure is increased. The machine will detect the smallest variation in the case size. If the case expands, even slightly, then the watch is not water resistant.

Wet Test – The watch is placed in a chamber which is half filled with water and half air. Air pressure is increased while the watch is out of the water, then the watch is slowly immersed into the water. Once the watch is completely immersed, the air pressure is slowly released. If bubbles come out of the watch it means that air entered the watch prior to immersion & the watch is not water resistant. This method is generally used as a second test to pin-point the problem area.

Units of Water Resistance based on pressure

Meters/Feet: This is the most common way of measuring the water resistance of a watch. 100 meters is just over 328 feet.

ATM: This stands for Atmospheric Pressure. At sea level, the ATM rating is 1, which is equal to 10 meters.

Bar: Bar is a metric unit of pressure named from the Greek word baros which means weight. It isn’t isn’t commonly indicated on a watch because meters/feet and ATM are more widely understood by the general public. 1 bar is equal to 100,000 Pascals, 14.5 PSI (Pounds per Square Inch) or 0.98 ATM.

Helium Escape Valve

The Helium Escape/Relief Valve is used only by deep diving expeditions when a diver operates from a diving bell. As the bell is lowered pressure begins to increases & helium is added to the breathing mix. Oxygen becomes toxic at a higher pressure, for example, pure oxygen would become toxic at 6 meters. Normal air would become toxic at the pressures technical divers and saturation divers usually work at. They usually use a mixture of three gases (Oxygen, Nitrogen and Helium), known as Trimix. Helium makes up a significant proportion of the mixture because it does  not have a narcotic effect on the body, therefore reducing the risk of nitrogen narcosis (the bends) from occurring. Not only this, but helium has a lower density than normal air which means that it is also easier to inhale under water.

The problem is that helium is one of the smallest molecules & will seep into the watch through the seals until the air pressure in the watch equals the air pressure in the diving bell. As the diving bell surfaces & decompresses, the helium molecules inside the watch expand, if there isn’t a valve then the pressure in the watch will pop the crystal off. To avoid this, Omega and Rolex developed their own helium escape valve systems which allow the helium to escape. Omega uses a second crown which screws closed on all Seamaster watches except for the Aqua Terra which doesn’’t have one and the Ploprof which uses the automatic helium escape valve design that is common on Rolex diving watches. Many brands use the escape valve in one design or another. Generally, the escape valve can be found on watches which have a water resistance rating of 300m or greater.

Interpretation of the Depth Ratings

Although a watch may be rated 30m/99ft water resistant, it does not mean that the watch can be immersed to that depth. The depth rating posted by the manufacturer is theoretical in nature and can only be achieved in a perfectly optimum environment of a laboratory – which is impossible to replicate in real life. It’s also important to consider that watches such as the Rolex DateJust and DateJust II models might well be rated to 100m and therefore great for swimming with, but they were not designed as full on diving watches and therefore may not survive prolonged experiences of over 50 meters. You should also consider any chemicals that might be in the water and whether they can react to materials used in the construction of the watch.

Water Resistance Guide

No rating (Dust proof/moisture proof) – 30m/99ft

Does not allow contact with water

30m/99ft – 50m/165ft

Allows for contact with water such as washing hands and rain

50m/165ft – 100m/330ft

Allows for light pool swimming and swimming to the bottom of the deep end

100m/330ft – 200m/660ft

Allows for swimming and snorkelling

200m/660ft – 500m/1650ft

Allows for impact water sports such as surfing and scuba diving

500m/1650ft +

Appropriate for technical diving

Obviously, the higher the rating, the more appropriate the watch is for deeper diving.

IMPORTANT: We strongly recommend purchasing a watch with a screw-down crown if you intend on wearing the watch while you are in contact with water.

Our Recommendations

  • Have your watch water-tested once a year.
  • Never open, wind or operate the crown while in water.
  • Never press the buttons of a chronograph watch while in water – unless otherwise stated by the manufacturer.
  • Do not subject your watch to extreme temperature changes.
  • Do not subject your watch to sudden & rapid air-pressure changes.
  • Do not allow your watch to come into contact with corrosive chemicals, such as abrasive soaps & highly chlorinated water.
  • Ensure that the crown is always pushed in, and if you have a screw-down crown make sure it is always tightened. Double-check before immersing in water.

What about the bath or a shower?

You must not wear your watch into the washroom if you have a habit of daily washing, even if it is a diving watch. The warm air in the room will cause the seals in the watch to expand, the temperature shock of when you step outside into the colder air of the rest of the building will cause the seals will contract and allow a tiny amount of moisture inside the case. Over a period of time between services this can cause the hands and dial of a watch to rust, even if the watch is rated at 300m or more.