The Backward Evolution of the Rotating Bezel

Not everything gets more complicated as it evolves. The bezel, once a simple frame around the glass of a watch, became an integrated mechanism before it evolved into a simple numeric scale. From alarm clocks, navigational computers, and slide rules it became the most-recognized feature of the most iconic watches. Let’s consider the history of the rotating bezel.

The simple rotating bezel was once very complex!

From Complex to Simple

We tend to think that innovation starts with simple ideas and becomes more complex over time. Surprisingly, the opposite is usually true. Lacking a clear use case, inventors tend to start with a complex concept before stripping away less-useful elements. Consider the Apple Newton, a full-featured handheld computer with dozens of innovative ideas that inspired simpler PDAs before morphing into the modern smartphone. My 2017 BMW i3 electric is truly an exotic car, built like a carbon fiber science project and entirely unlike the conventional 2027 i3 sedan.

The same is true in watchmaking, and this brings us to the humble rotating bezel. Nearly every brand has a dive watch styled after the Rolex Submariner with a bold black knurled rotating bezel marked with triangles, sticks, and numerals. Most buyers never give these a second look, let alone turn them to time a drive, let alone a dive. Some brands also make a watch styled after the Breitling Navitimer with a busy two-part bezel marked with confusing aeronautical indications of speed and fuel load. Rolex even created a functional rotating bezel for the 2012 Sky-Dweller, used to select different functions.

A bit of research reveals that the history of the humble rotating bezel runs exactly counter to expectation, beginning with functional complications before proceeding to obscure slide rules before being stripped down to a basic hour indicator. It took 50 years for the rotating bezel to be simplified enough to enter the public consciousness and that long again before Rolex invented the Sky-Dweller’s ring command. Like so many innovations, there’s a lot to learn if you look into the rotating bezel!

The Functional Bezel

This 1913 catalog image shows a modern pocket watch with a knurled screw-on bezel

The bezel itself was an innovation. Most early clocks and watches were “open faced”, but by the 17th century some included a glass to protect the dial and hands. This was mounted in a frame of metal called a bezel, which was often attached to the case with a hinge. Thus, the first bezel was a functional part of the case, if not the watch movement.

Watches in the 19th century adopted setting and winding using a crown and often had a fixed glass over the dial, since the hands no longer needed to be manually manipulated. The glass was set directly into the rounded case without a separate bezel. This gave the watch a smooth curving contour that felt in the hand like a bar of soap (“savonnette” in French). Some watches still featured a bezel around the glass, notably the screw-on bezel and back produced by Keystone and others in America.

Winding and setting functions were not unified in a single crown until the 20th century. Earlier watches often had keys for winding or were set manually by rotating the hands. Pendant winding using a crown became widespread in the 19th century, and inventors were constantly working to enable hand setting by rotating the crown as well. These often involved levers or buttons, but some involved a rotating knurled bezel very similar in concept to the modern Sky-Dweller.

Eterna’s pioneering alarm wristwatch used a rotating bezel to set the alarm time

As alarm watches became popular in the early 20th century, a question arose about how to set this additional function. Attention again turned to the bezel, which could be rotated to set the time of the alarm. This must have been fairly common, as 1907 coverage of a new alarm watch from F. Schweizer & Cie discusses the limitations of bezel-set alarms (reliability and accuracy).

This was notably used by Eterna on their innovative if unsuccessful 1914 Cal. 68, the first alarm wristwatch. This 13 ligne movement was offered in a small pocket watch, a wristwatch, and a convertible watch that could be mounted on the steering wheel of a car. Although the wristwatch didn’t sell well, Eterna used the same movement in a line of successful travel alarm clocks, and these inspired the entire industry to adopt this mechanism.

Soon, most alarm clocks used a rotating bezel to set the time, often with an indicator on the bezel to show the current setting. This complicated mechanism was the first widely-used rotating bezel, pre-dating the dive watch craze by three decades.

The Harwood Perpetual used a rotating bezel to set the time, with an indicator that this function was active above 6 on the dial

A similar system was employed by John Harwood to set the time his Perpetual, the first self-winding wristwatch. The primary driver for his invention was the need to prevent dust and moisture from damaging the movement, a common issue on the battlefields of World War I. Since sealed crowns and stems had not yet been developed, Harwood’s goal was to create a sealed case with no crown, and he was inspired by the alarm clock setting mechanism created by Eterna to use a rotating bezel to set the time.

The Harwood Perpetual was a global sensation, even if it ultimately did not find many buyers. And the knurled or fluted bezel became a common look in the 1930s, adopted by other waterproof watch cases like the Rolex Oyster. Although not a rotating bezel in the strictest sense, many of these could be unscrewed to access the hands, dial, and movement during assembly and servicing.

This 1953 advertisement calls out Perrelet and Harwood as inspirations for Rolex

It is easy to see how the Harwood Perpetual inspired the legendary Rolex Oyster Perpetual, and Rolex agreed: They specifically cited Harwood along with Abraham-Louis Perrelet as inspiration for their Oyster Perpetual in a series of advertisements in the 1950s. And it wasn’t just the Perpetual name or centrally-rotating winding: Rolex popularized the rotating bezel in this same time period, introducing the Turn-o-Graph, Submariner, and GMT-Master, as we will discuss in a moment. All of these feature a bezel that strongly resembles the Harwood Perpetual.

Lindbergh, Longines, and Weems

The idea that a rotating bezel could serve as an indicator of information rather than a mechanism to set the time originates with American aviator Philip Van Horn Weems. He developed a simplified navigational system for aircraft while serving in the American Navy in the 1920s and early 1930s. His system relied on a so-called “second-setting watch” featured a rotating inner dial that could be set to a time signal over the radio. This was based on Longines’ 1918 Touran pocket watch, which was designed to be re-set to zero at sunset to approximate the Alla Turca timekeeping system of the Ottoman Empire.

This 1932 article in Journal Suisse d’Horlogerie outlines the use of the Longines Weems-Lindbergh Hour Angle Watch

A close collaboration between Weems, aviation pioneer Charles Lindburgh, Longines-Wittnauer director John P.V. Heinmuller, and the Longines and Fluckiger factories in Saint-Imier resulted in a revolutionary watch that allowed pilots to determine their location using markings on a rotating bezel. This began with a specially-modified version of the Touran watch with an outer chapter scale showing units of arc, delivered in 1930. In 1931 Longines added a rotating bezel marked with units of arc in red and green. This bezel would be pre-positioned according to the equation of time table to instantly perform the calculation needed to determine the Greenwich Hour Angle of the Sun.

Once Longines developed a stop-seconds flyback movement the inner rotating dial component was no longer needed, allowing all calculations to be performed using the rotating bezel. Later versions even dispensed with the units of arc markings on the bezel, using a simple scale with units marked 10 through 60. These were no longer Hour Angle watches at all, but they were some of the first watches with a rotating bezel. In later decades Longines produced faithful reproductions of the Lindbergh Hour Angle watch, including a lovely limited edition in 2018.

The Evolving Chronograph Bezel

As the world industrialized in the early 20th century, a need for time measurement appeared. Businesses were more interested in tracking efficiency, and aviators needed to record and note time of travel. Watchmakers struggled to develop affordable and reliable chronograph mechanisms in the 1930s and 1940s, and this a fascinating area of study. This was the era when the old monopusher gave way to the Compax, flyback, and chronostop.

Heuer’s 1935 aviation chronograph featured a rotating bezel to mark elapsed time

The alarm time indicators of previous decades gave innovators a new idea: A rotating bezel could set an indicator to measure elapsed time. In 1935 Heuer introduced a new chronograph for aviators that featured a knurled rotating bezel attached to a white triangular indicator “to mark the departure time or any other observation.” It is unclear if this is the first chronograph watch with a rotating bezel, but it is the earliest our research has uncovered.

Breitling produced a similar-looking aviation watch with a rotating bezel in early 1936. Unlike the Heuer chronograph, the Breitling model has no minute totalizer, only chronograph seconds. As noted in Journal Suisse d’Horlogerie, the bezel indicator would “serve as the minute totalizer”, synchronized with the running minutes hand for timing flight operations.

This 1936 Breitling aviation chronograph is very similar to the Heuer model This 1936 Fortis chronostop has a fully-marked bezel

Fortis also produced a chronostop watch with a rotating bezel in 1936. This movement had a stop and reset function for the central chronograph seconds hand using a pusher in the crown. The Fortis chronostop was the first watch we’ve seen with a full set of 60 markers on the rotating bezel, complete with numerals from 5 to 60. The design also departed from the classic rounded screw-on bezel look: It has a flat bezel that aligns with the dial along with a sharp vertical knurled edge.

In 1938, Damas added the now-common triangle at the top, along with a fully-marked bezel

The 1938 Damas Ref. 2452 dispensed with the expensive chronograph movement entirely, relying solely on a rotating bezel and central running seconds hand to record elapsed time. This watch advanced the bezel markings in a significant way: It features a triangle at the top rather than 0 or 60. This is a common design today, combining the Heuer and Breitling bezel indicator with the full minute track and vertical edge seen on the Fortis chronostop.

The 1940 Invicta Secontrol (left) and Time-Log (right) featured a 12-hour bezel with steep grooves

The next major advancement in bezel design came from Invicta, then a respected maker of complicated watches in La Chaux-de-Fonds. They introduced two models for 1940 with a deeply-grooved 12-hour bezel: The Secontrol had a chronostop movement and telemeter and tachymeter scales on the dial, while the Time-Log used a start-stop chronograph movement with three pushers. The new bezel served as an hour counter for these watches, which would be much more useful in association with the minute totalizer subdial on the Time-Log. It is unclear exactly how the 12-hour bezel would be useful on the Secontrol.

Minerva’s 1949 Ref. 1527 introduced the count-down bezel

The next important advance in simple bezel design came in 1949 with the Minerva Ref. 1527, which features numerals that count down rather than up. This is useful as a reminder for future events rather than a recorder of elapsed time. Since this model is marked from 1 to 11 (again with the triangle at 12), it was designed to be used by aviators to mark the next turn using the hour hand. Count-down bezels are uncommon today but they remain an interesting variation on the theme.

The Slide Rule Bezel

The slide rule (“règle à calcul” in French) was invented by English mathematician and clergyman Reverend William Oughtred and others in the 17th century, utilizing the mathematical concept of logarithms discovered by John Napier. Logarithms exploit the relationship between two scales to perform various calculations, especially multiplication and division. Slide rules were the most convenient and accurate mathematical tool until the creation of electronic calculators and computers in the 1960s.

Although Moret called his invention a “montre à calcul”, it was a calculator rather than a watch

The straight slide rule is most familiar but the circular slide rule has existed since the 19th century. In 1905, Emile Alexandre Moret of France received a patent for a mechanical calculator that used geared hands to perform logarithmic calculations using circular disks. Moret recognized that a circular slide rule could be packaged as a clock or watch, calling his invention a “montre à calcul”, but it did not include a timekeeping function.

Fabriques des Montres Zénith patented a pocket calculator resembling a watch in 1918

Zénith, the famous Le Locle watchmaking firm, received a patent for a mechanical slide rule calculator in a pocket watch case in 1918. Once again, although this resembled a watch it was actually a pocket calculator without any timekeeping capability.

Importantly, both of these designs appeared before the Harwood Perpetual watch popularized the concept of a rotating bezel. It was only a matter of time before someone moved the circular slide rule to the bezel of a watch.

Graef & Cie, Fabrique Mimo, was one of the most innovative watchmaking companies in the first half of the 20th century, introducing many firsts between 1930 and 1941: The first wristwatch with a calendar, a double-barrel 8-day movement, a digital jump-hour display, and even a quick-change strap. So it is no surprise that Mimo was also the first company to produce a wristwatch with a slide rule bezel.

The 1941 Mimo-Loga was the first watch with a slide rule bezel

The Mimo-Loga was the first watch to feature a freely-rotating bezel, and it included classic slide rule markings. The July 27, 1940 patent eloquently describes that, “in addition to the chronometric and chronograph devices, includes at least two conjugate logarithmic scales, at least one of which is mounted on a rotating member concentric with the dial that carries the other.”

The Mimo-Loga was introduced in early 1941, just before Mimo founder Otto Graef retired. He left his sons in control of Mimo to his sons, but they were more interested in re-establishing the famous Girard-Perregaux brand, which the family acquired in 1928. Despite its history of innovation, the Mimo brand soon disappeared.

One watch comes to mind when we think of the slide rule bezel today: The Breitling Navitimer. Although Breitling is correctly credited with making the slide rule bezel famous, it was introduced with the Chronomat, not the Navitimer, and just a few months after the Mimo-Loga! Let’s set the record straight.

Breitling advertised the Chronomat with its innovative slide rule bezel in September of 1941

Most contemporary accounts claim that Breitling introduced the Chronomat in 1942, but primary sources include advertisements for “Le Chronomat” in September 1941. Although the watch may not have entered production this early, it was clearly a focus for the company at this time. Like the Mimo-Loga, the Chronomat had slide rule markings on the rotating bezel. But Breitling’s watch used a chronograph movement, and this allowed the wearer to perform many more useful calculations.

Breitling produced a companion booklet to help buyers make the most of the Chronomat’s capabilities. The dial also included red reference markings to assist in measuring seconds, fifths, minutes, and hours as well as a telemeter indicator. The Chronomat was specifically designed as a tachymeter, telemeter, pulsometer, and metronome, and the scale could perform standard mathematical calculations like previous circular slide rules. Breitling even produced a cardboard cutout model, available to retailers to help demonstrate these functions.

The Chronomat name combined these capabilities, “chronograph” and “mathematics”, but this did not last long. An automatic Chronomat without a chronograph function was introduced by 1954 and the famous Chronomatic movement further muddied the waters. Today the Chronomat line includes many chronographs but not one has a slide rule bezel.

Breitling began advertising the Navitimer in 1955

This brings us to the most famous slide rule watch, the Breitling Navitimer. Today, the company claims that this watch was created in 1952 and released in 1954 with AOPA branding, and we have no reason to doubt their internal records. But the earliest public references to the Navitimer appear in 1955, and the trademark for the name was received on January 22 of that year. The Navitimer is a specialized watch, originally exclusively available to pilots, and may not have been publicized or even named until 1955.

While the Chronomat had indicators for various capabilities, the Navitimer was designed specifically to perform specialized calculations related to air travel: Ground speed, distance per minute, fuel consumption, rate and distance of climb or descent, and nautical and statute mile conversion. These scales and indices made for a very busy dial despite the hefty 41 mm case. Breitling’s current lineup includes a variety of beautiful and colorful interpretations of the classic Navitimer.

Incredibly, it is this specialized tool watch design that has become dominant in the public consciousness. Today there are numerous “Navitimer” style watches made by brands like Casio, Citizen, Hamilton, Seiko, and Victorinox. The Sinn 903 also deserves special mention: They bought up the remaining Navitimer stock from Breitling in 1979 and continued to sell these original watches as their Navigation Timer into the 1980s. This has remained in production today, with the Model 903 II released in March of 2024.

Rolex: Turn-o-Graph, Submariner, and GMT-Master

When the Swiss Industries Fair in Basel opened on May 8, 1954, visitors to the Rolex stand were treated to three new product releases: Explorer, Submariner, and Turn-o-Graph. These watches marked a transition for Rolex and ultimately the entire watch industry. All three were tool watches with modern Oyster cases and Perpetual movements, and two were defined by their distinctive rotating bezels.

The Rolex stand at the Basel fair in 1954 Europa Star’s coverage of the 1954 Basel Fair emphasized three new tool watches from Rolex

The Turn-o-Graph name is not well-remembered today, but it was a staple of the Rolex lineup (on and off) until 2011. It was a simple time-only watch with a rotating bezel designed to calculate elapsed time. The Rolex rotating bezel was mostly flat, with a sharp knurled edge. In the Turn-o-Graph it was marked with four dots then a stick or numerals at 10, 20, 30, 40, and 50. A triangle with a luminous dot was placed at the top. This design reflected the dial, which used dots on the hour, sticks at 3, 6, and 9, and a triangle at 12, all with luminous paint. The Turn-o-Graph was thus the most harmonious of the trio.

The Submariner was very similar to the Turn-o-Graph but was rated to 200 meters. Rolex had a long history of producing waterproof watches, but the Submariner was altogether more elegant and refined. The bezel was wide and flat, lacking the dots of the Turn-o-Graph, with stick markers alternating between numerals on the 10s. Although a true icon today, this original Submariner looked like nothing else on the market at the time. The look was soon copied by the entire industry, making the simple flat rotating bezel a sports watch staple. And the Submariner is undoubtedly one of the most in-demand watches globally to this day.

On March 22, 1956, Rolex founder Hans Wilsdorf gathered friends and industry figures to the Hôtel des Bergues in Geneva to celebrate his 75th birthday and the success of the company. Along with the “Stick-o-Matic”, presented to him by the factory, the crowd was able to see a brand new Rolex model.

I’ve wanted to highlight the Rolex Stick-o-Matic for years! The original GMT-Master is another Rolex icon

The GMT-Master was developed with the needs of pilots in mind, though Rolex did not go to the same extremes as the Breitling Navitimer. It was the first Rolex to feature a 24 hour hand, though it was not adjustable until the 1983 GMT-Master II. And it also included a date window under a magnifying glass bubble at 3 on the dial. But it is the rotating bezel that we will focus on, since that is the subject of this article.

Mechanically quite similar to the Submariner bezel, the GMT-Master featured alternating dots and numerals from 2 to 22, indicating the hours for the central 24 hour hand. In this way, it could be used to show the time in a second time zone by rotating the bezel ahead or behind the fixed hand. This too would become an iconic design, copied by many other firms in the coming decades. And it remains a favorite Rolex model today.

From Complex to Simple, With Many Variations

There is far more we could say about the rotating bezel, but perhaps this is enough to prove my point: Invention often proceeds from complex to simple. What was once an integrated mechanism to set the alarm or time became a simple alternate time scale. But there is subtlety to the rotating bezel! While most count up, some count down. While most are marked at 60 minute intervals, others are marked at 12. And some function as slide rules or perform complicated calculations specific to navigation. The simple bezel is far from simple, and many different companies and inventors were involved in its evolution!

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