History of the Bezel
In the 1950s, it was decided by watch manufactures that the bezel was the perfect place to add in functions without complicating the watch movement.
Technical bezels had been on watches since the 1930s. In particular, Rolex put a rotating bezel on the Zero-graph, a very rare timepiece. Since then, the rotating bezel has become a staple on all dive watches. It even made its way into the ISO 6425, the international standard governing what can be considered a dive watch.
Images courtesy of Phillips.com
Longines is another brand who decided to use a bezel with a scale. Charles Lindbergh made a non-stop Atlantic crossing and his Longines was a navigational instrument. An internally rotating bezel was used so it could be set and kept accurate while listening to beeps over the radio and aligning the dial to the signals. The Longines Legend Diver is a tribute to the classic 1960’s Dive Watch with internally rotated bezel, similar to the Lindbergh.
World War II helped shape the design and technicality of bezels. The resulting period of military watches witnessed luminous dials as well as aviation timepieces with slide rule bezels and a GMT function.
Types of Bezel Scales
Tying in with the amount of different functions on a watch, there are quite a few different types of bezels and bezel scales. Some scales are found on the top of main bezel and can rotate unidirectional or bidirectionally. Dive watches will sometimes feature the bezel internally controlled by an additional crown. This feature avoids accidental bumps, which can lead to errors in calculations.
However, some scales aren’t found on the top of the case but rather around the outer edge of the dial. Instead, they open up the main watch bezel for more case material with a smooth finish. Nevertheless, it still performs the same calculations no matter where the scale may be found.
Plain and Fluted Bezel
Not all bezels serve a technical function, featuring a scale or numbers. Instead they show the design of the watch with historical influences. These watches are typically time or date only and will feature the classic metal bezel, which is smooth. In some cases, this bezel is also fluted, paying homage to vintage watchmaking. This refers back to when fluted part would be used as a grip to be removed from the watch.
Clockwise from top left: Diamond Bezel on Vacheron Constantin Overseas, Smooth Bezel on Omega Aqua Terra, Fluted Bezel on Rolex Sky-Dweller and Smooth Maltese-Cross Bezel on Vacheron Constantin Overseas Chronograph.
The size of these bezel can vary from a thin strip of case metal circling the dial to a thicker piece of metal surrounding the crystal. In addition to being plain or fluted, some brands take advantage of this space and add diamonds for certain models.
One of the most common scales seen on the outer ring of the dial or on the bezel, is the tachymeter or tachometer. What is a tachymeter? It is a scale on a fixed, non-rotating bezel, which calculates units per hour for chronograph watches.
As you look at the scale, you see it starts around the 7-second mark at 1000 and finishes at the 12 o’clock mark with 60. This means it can measure times from 7 seconds to 60 seconds.
It is possible to use this type of scale to measure speed or distance, but some measurements may require more mathematical equations than others.
Learn how to use a tachymeter in our comprehensive guide!
Pulsometer Rated to 30 Pulsations
The pulsometer is one of the rarer scales included on a watch. This is typically found on a medially-designed watch and worn by doctors.
This type of addition dates back to the 1920s when doctors needed to accurately measure the pulse of a patient. Similar to the tachymeter scale measuring units per hour, the pulsometer measures heart rate within a minute. The scales are calibrated from 15 to 30 pulses around the dial, starting around the 5 second mark at 200.
Doctors would start the chronograph and count the beats up to what their watches were rated to and then stop the chronograph. When they stop, they would be able to read the heart rate in beats per minute based on where the seconds hand lined up on the pulsation scale.
Also similar to the tachymeter is the telemeter, which can also be mistaken for the former due to their similar names! This type of scale is less common and is used to measure the distance between a visible event and an audible event.
The best way to describe this type of scale is by looking at a thunderstorm. For instance, you would start the chronograph when you see the lightning flash and start it when you hear the thunder. The chronograph will lay atop the distance, typically measured in kilometers.
Decimeter / Decimal Bezel
Offered as a custom alternative to tachymeters on Speedmasters, the Decimeter or Decimal bezel is a somewhat rarer scale. Not to be confused with the unit of length of the same name, Decimeters allow the wearer to translate time into decimal values.
It can be easily recognised by the distinctive 100 scale that is primarily used for scientific and industrial measurements. In combination with the chronograph, a time measurement can be easily converted into a decimal or percentage for use in longer calculations.
For instance, the 6 o’Clock position reads at 50, which can be translated to either 50% or 0.5 of a minute. While some rounder time stamps are easy to proportionately convert into decimals, this tool renders the task relatively simple for more complex time readings.
GMT / Greenwich Mean Time
The GMT function stands for Greenwich Mean Time and is also known as UTC or Coordinated Universal Time.
Most watches with a GMT complication added will have a large rotatable bezel outside of the crystal with a 24-hour ring, just like the Rolex GMT Master II BLNR. Nevertheless, it is possible to have a GMT without the rotating bezel. In this case, the 24 hour ring will be planted around the rehaut between the indices and the edge of the dial. The Grand Seiko GMT SBGJ001 has this type of 24-hour scale.
In both cases, the GMT hand circles the dial, making one full rotation in a 24-hour period. For watches with a rotating bezel, they sometimes feature two colors designed to showcase day or night hours. A rotating bezel also allows for the use of a third timezone if needed.
Watches with an internal 24-hour ring will be read the same way. The GMT hand lines up to the 24-hour scale and then the minutes are read through the central minute hand.
The count up bezel is most commonly found on a dive watch for calculating elapsed time. It features a scale from zero to 60 around the bezel, aligning with the minutes in the hour. The first 15 minutes are typically marked with one minute increments, sometimes this extends to the first 20 minutes.
After the minute markers end, the rest of the bezel is marked in five minute increments. This is specially designed to avoid running out of air during a dive.
Furthermore, the bezel will be unidirectional and only rotate counter-clockwise. This means that if you bump the bezel while diving, you can only have less time and more air in your tank.
To use this bezel style, you set the zero marker, typically identified with a triangle and large luminous dot, with the minute hand at the start of your dive. As time passes you read off elapsed time on the bezel, with the first 15 minutes individually tracked.
Similar to the count-up bezel is the countdown scale. The countdown bezel scale measures the time remaining in an event, either before the event begins or after it has started. This scale is reversed on the bezel, going from 60 around to 0 clockwise. Typically the countdown bezel has a bidirectional bezel which makes this inadequate for diving.
To use this type of counter, you rotate the bezel so that the time remaining is set to the minute hand. When the minute hand then reaches zero on the scale, the timer is done. The last 15 minutes are highlighted to bring attention to them.
A yacht-timer is mainly used in regatta racing or yachting. Typically, along the outer edge of the bezel, there is a timer from 10 to 1 spanning across the top 2/3 of the bezel. However, different brands create the timers in different styles.
In boat racing, a horn signals the start of the countdown to race time. The goal of the crew is to avoid going over the starting line before the second signal starts the race. Typically, the timers will indicate the time remaining to the actual start of the race.
One of the most complicated and misunderstood bezel scales on a watch is the slide rule. This type of scale helps you multiply and divide. The feature was made popular by Breitling in the 1950s when they released the Navitimer.
The scale allowed for pilots in the 1950s to calculate fuel consumption, air speed and distance and include metric to standard conversions. Still today, pilots are taught how to use the slide rule.
However, most people outside of this profession don’t know how to use the scale. As Breitling understands that this feature is not typically known how to use, they released a comprehensive user-manual.
There are many different uses for different types of bezels. Each scale calculates something different and is unique to that style of watch, whether it be for diving, racing or aviation.
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