What Makes a GMT Watch?

Following George’s excellent Ultimate Guide on How to Use a GMT Function on a Watch, we will be discussing the visual and technical features of GMT timepieces and the different types of GMT watches one can buy in 2022. There have been a lot of talks going around the watch community regarding “caller” versus “true” GMT calibers. Regardless of how the movement works, a GMT basic function is to make it possible to track a second or third time zone. In that spirit, we will first be discussing what makes a GMT watch and then the different options available at various price points.  

Source: @mainspring.watch 

Caller vs. True GMT 

The very first GMT was created by Rolex in 1954 in the GMT Master reference 6542 and the caliber 1036. This watch was created for Pan Am to make it possible for their pilots to track two time zones while traveling across continents and timezones. The first GMT Master did not have an independent local hour hand unlike the later GMT Master references—and in particular, the GMT Master II introduced in 1983. The caliber 1036 had a GMT hand attached to the hour and minute hands and one had to rotate the bezel in order to point the GMT hand to a different timezone (in other words, the GMT hand could not be independently set.) Things have changed a lot since, however, and a GMT hand can be set separately from the local hour hand. 

Source: www.lepetitpoussoir.fr 

What people commonly refer to as a “True GMT” is when the local hour hand can be set independently from the other hands. The purpose for this is simple: pilots set the GMT hand to their home time following the Greenwich Mean Time scale—the time reference used by all pilots across the globe—and simply change the local hour hand when they arrive at their destination without having to hack the movement. (The GMT reference time will remain the same wherever they are in the world.) This means the watch keeps running while one changes the local hour hand. That is the definition of a “True GMT” watch. 

What is then a “Caller GMT?” Well, it’s one where the GMT hand is set independently and that’s the one that “jumps” in one-hour increments around the dial. Most GMT watches available under the $2,000 price tag are “caller” GMTs and not “true” GMTs. Although recently, the Japanese movement manufacturer Miyota released a True GMT caliber that can be seen in watches for less than $1,000. But the movement alone doesn’t make a GMT watch, as we will see below. 

Source: www.wornandwound.com 

Features of a GMT Watch 

As mentioned with the Rolex GMT Master I and II, GMT watches come with a bezel that displays a 24-hour scale. The GMT hand (the fourth hand of the watch) points at the bezel to a different time zone. Generally, these bezels display the second time zone by highlighting the even hours with Arabic numerals and the odd hours with dots or hash marks. Some brands do the opposite. As it is the case with the Rolex GMT Master collection, the bezels are often sub-divided in two sections, making it possible to highlight the nighttime hours (between 6pm and 6am) in one color and the daytime hours (between 6am and 6pm) in another one.

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If one wants to keep track of two additional time zones instead of one—and not spend more than $10,000 on a modern GMT Master II—then one can buy a watch that has a second 24-hour scale printed on the rehaut. This is the case of the recently released Seiko GMT 5 collection (pictured below) as well as the previous generation of the MONTA Skyquest. Having two 24-hour scales makes it easier to track time in a total of three time zones, however it is the GMT hand that can be set separately, not the local hour hand. 

Because GMT watches are practical tools used by pilots (at the beginning) and anyone (now) they often come with a date function. Although some GMTs don’t have a date, I find it odd to indicate the time in a different time zone (in which case it could mean the day prior or after our current time) without indicating which day of the month it is. But that is just me and I recognize and respect people’s preference for symmetrical dial designs with no date aperture. 

Last but not least, brands generally color-code the GMT hand to look different than the local hour hand. Interestingly enough, oftentimes it is the GMT hour hand that looks more prominent than the local hour hand. This is common with Rolex, Omega, and Grand Seiko that highlight the GMT hand with a bright color, for example red or orange. I guess it makes it easier to distinguish the time in a second time zone. I’ve not yet seen a good example of a brand making three time zones easy to read as reading the hour on an inclined reheat is not always easy. 

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MONTA’s Atlas and Skyquest 

A special note should be made of MONTA’s two GMT watches that display the second time zone differently. The Atlas displays it on the rehaut using a prominent typeface while the Skyquest (the second version) displays the GMT time on the bezel. The previous version of the Skyquest displayed two additional time zones, one on the bezel and one on the rehaut. What MONTA offers 2022 is two options for GMT watches to match people’s personal affinities for horology. 

Source: www.chrono24.fr

While the Atlas is more of an elegant everyday timepiece, the new Skyquest looks and operates more like a proper tool watch. (I would even go to the length of saying that this is what the 1950s Pan Am pilot watch would have looked like if it would have been created in 2022 by MONTA and not Rolex.) In a way, MONTA is one of the few (if not rare) brands to offer two GMT watches that display a second time zone in two very different ways. 

Other Options 

Both well-established and recently created brands offer different options for GMT complications. Since Seiko released the Seiko 5 GMT line, many independent brands have jumped on the bandwagon to create sub-$500 GMT watches. And if one does not want to buy a Rolex GMT Master II or a Grand Seiko GMT Spring Drive, one can look at  Omega’s Planet Ocean Co-Axial Chronometer GMT or Mido’s Ocean Star GMT. Lastly, there are plenty of affordable quartz-powered GMT from Timex, Casio, and microbrands available on the market.  

Source: @mainspring.watch 

Final Thoughts 

GMT watches have become very popular over the past few years and it is nice to see independent brands such as MONTA add these types of complications to their catalogs. This makes it possible for those who have the souls of explorers and a yearning to travel to acquire a good quality GMT timepiece that is both robust and elegant, in a way keeping the tradition with the first Rolex GMT Master that came in with a case of 38mm. (This size felt big in the 1950s but modest in 2022.)

Featured image: www.lepetitpoussoir.fr