A watch bezel is the part of the watch that surrounds the crystal, and it can be decorative or functional. Sport and tool watches, like diving watches, racing watches, and military watches, were designed to serve specific purposes, and they often have special bezels that allow the wearer to measure specialized units of time for a specific purpose. For example, a diver can use the bezel to measure the amount of time left for the air in her oxygen tank, or a racer can use a tachymeter to easily calculate speed. Sport watches have become increasingly popular in everyday fashion, and so the purpose of the tool bezels is less understood. Here’s the Secrete Fine Jewelry guide to understanding the different types of watch bezels.
Dive watch bezels
A dive watch bezel is classified as a “count up” bezel with a scale from 0 to 60, indicating the minutes in an hour that allows divers to time their dives safely. Dive watches have unidirectional bezels, meaning they only spin one way, to prevent accidentally knocking the bezel in the wrong direction that would potentially lead you to believe you had more time (more air) than you really did. With a unidirectional bezel, if knocked, you could possibly believe you had less time than you really did, but coming up with air left over is definitely better than running out of air.
Right before submerging, the diver turns the bezel to the position of the current time’s minute. As time elapses, you can clearly see how long you’ve been underwater by looking at where the minute hand points to on the bezel. Some dive bezels are marked every minute, making it easier to time a slow ascent (to prevent the dangers of surfacing too quickly), while others are only marked minute by minute for the first 15 minutes, like the Rolex Submariner. Some divers reset bezels like the Submariner bezel when they’re ready to ascend so that they can accurately time slow resurfacing.
Sailing watch bezels
A “count up” sailing watch bezel is similar to the dive watch bezel, with the exception that it is bidirectional. Meant to be used for timing regattas, water-resistant watches like the Rolex Yachtmaster look similar to dive watches, but their different purpose is evident in the bezel function. The bezel can be set to a start time to measure how much time has passed, just like the bezel on a dive watch. Because the bezel turns both ways, however, it would be dangerous to use it to time a dive where an accidental knock in the wrong direction could mislead the wearer into believing he should stay underwater too long.
A “countdown” sailing watch bezel is a much more complicated animal. Developed in 2007 by Rolex for the Yachtmaster II, this bezel indicates a programmable timer that can be synchronized with a regatta timer to count down up to ten minutes. Set with the bezel and measured with pushers and hands that are similar to a chronograph function, this is useful for counting down to regatta start times.
24 hour bezels/ GMT
24 hour bezels can be fixed (unmoving) or rotating. A fixed 24 hour bezel is used to tell GMT. A GMT hand on the dial points to Greenwich Mean Time on the bezel.
GMT is the international standard for time zones. All other time zones are designated based on their relative position to GMT. GMT watches were originally developed for aviation, as pilots can travel through many time zones in a day, it’s useful to have the one “true” time clearly on display. Many people who casually wear GMT watches, like a Rolex Explorer II, may choose to display a second time that is more useful to them– displaying the times of both their east coast and west coast offices, for example.
A rotating GMT bezel is a 24 hour bezel that can either be left positioned like a fixed bezel to point at the 24 hour GMT time, or it can be adjusted to calculate a third timezone. This feature was developed by Rolex for the GMT Master in collaboration with PanAm airline to help pilots keep track of a home time, GMT time, and a third time zone where they may be travelling.
Tachymeters
A tachymeter is a feature of a race style watch that allows you to easily calculate speed over a fixed distance, like a lap on a course. Using a chronometer, the stopwatch feature, you can measure how fast an object (car, boat, horse, motorcycle, etc) was travelling in units per second. Where the chronograph hand stops, there will be a corresponding speed on the tachymeter bezel. Watches like the Omega Speedmaster have tachymeters to help calculate speeds easily.
Telemeters
Telemeter bezels are similar to tachymeters, but instead of calculating speed, they calculate distance based on the speed of sound. Say you see a bomb drop from an airplane and watch the explosion, then you hear the explosion, the delay in time between seeing and hearing can be calculated to represent distance. If you’re in a war zone, you probably won’t want to remember your high school science class notes on the calculations to figure out how far away it was. Telemeters are found on vintage style military watches, like the Junghans Meister Telemeter.
Pulsometers
Pulsometers are medical bezels developed for doctors and nurses, often for times of war when field medics had to do quick calculations without having to carry along much equipment. The bezel indicates a calibration number (normally between 15 and 30), meaning the number of heart beats the medic counts to. When the medic finishes counting, the pulse rate will be the number that the second hand points to on the bezel. Watches like the Flying Doctor Oris limited edition feature this medical-military technology.
Other bezels
There are other specialty watch bezels designed to calculate specific measurements, like slide rules, or to assist in navigation, like compasses. For most of us, we’re lucky enough never to have the occasion to need to assess vital signs on the battlefield or to calculate how far away a bomb is based on its sound, but we may very well find ourselves enjoying a day at the racetrack, a friendly regatta, or a SCUBA vacation. Many of us will appreciate knowing the time in another time zone as we travel and reach out to our loved ones.
No matter how often we do or do not use the tools on our watch bezels, we can only appreciate the ingenious technology that went into the design and mechanics by learning to use them. Perhaps we’ll take pleasure in using our telemeters during a stormy summer night while watching the flashes of lightning and listening to the approaching thunder, all the while tracking the location of the coming rain. No matter how much or how little we use these precision tools, they contribute to our love of horology, our appreciation for the rich history of innovators who created these functions, and our joy in wearing our favorite watches.
To learn more about watches or to try some of these amazing tools in person, stop by Secrete Fine Jewelry’s DuPont Circle store or contact us today.
