How technology has changed in the last hundred years. If you were to ask someone under the age of twenty what the disk icon on the save button means, or to explain why pumping your fist in a circle indicates lowering a car window, you’d probably be treated to a blank expression and perhaps a polite but firm request to stop asking stupid questions, but nevertheless—floppy discs and manually wound windows were barely a few decades ago. Imagine, then, how out of touch we must be with technology from the 1950s …

This is Rolex’s most recent addition to the GMT-Master stable, the 126710BLRO, an amalgamation of all the little details that have become synonymous with the brand’s pilot’s watch, plus a few modern sprinklings.

It’s a handsome, well-made thing, nicely proportioned with a good weight and a sense of quality that isn’t too formal. It’s easy to see why it’s such a popular choice, especially with that pop of colour. And it’s a look we’re very familiar with, the design having been in constant production for the better part of a century; we’re so acquainted with it, in fact, that it’s lost a little bit of what makes it what it really is.

Let me explain: back in the 1950s when the GMT-Master was conceived, barely a few decades had passed since the first person had flown across the Atlantic. Air travel, and the technology behind it, was booming as heavier-than-air flight became a reality. Even as the 1930s came to a close, the first transatlantic passenger planes were already taking to the skies.

To put that into perspective, the time to go from the first ever crossing in a flimsy single-seater to crowds of people being hauled over in full-on passenger planes was the same amount of time between hurricane Katrina and now. This was a period where the introduction of electricity was still a recent memory, punched card computers were new and exciting, and the first rocket that could reach space was still to come.

In this era of incredible technological acceleration, suddenly the world became a lot smaller. This was still a long while before Coordinated Universal Time, and so the problem of multiple time zones and the confusion of day and night on a 24-hour clock became rather apparent. It was one of many growing pains for a world that had flipped from taking days if not weeks to navigate, to mere hours.

It was also a time when Rolex was attempting to demonstrate its worth as a supplier of professional instruments, and this booming transatlantic aviation industry was exactly what founder Hans Wilsdorf had in mind when he made this, the GMT-Master 6542.

In developing a watch for transatlantic pilots, Wilsdorf approached aviation company Pan-Am to find out what it was they needed most. It seems obvious with hindsight, but the simple ability to know the time where you’re going—or where you’ve been—and whether it’s day or night was a massive benefit. Even outside of the cockpit, pilots’ body clocks were so out of whack that an easy reminder of home and local made all the difference.

It wasn’t as straightforward as just making a new watch, however; Wilsdorf had a lot of bases to cover to better his chances of success. Not wanting to put all his eggs in one basket, he developed a foundation for his many ideas with the Turn-O-Graph, an evolution of the DateJust with a customisable rotating bezel. So, although a ground-up watch with an independently adjustable sub-dial would probably have been a better bet for Pan-Am pilots, it didn’t fit the Rolex mould—quite literally.

Wilsdorf needed a simpler, cheaper solution, something he could build onto his existing platform with minimal changes. The result, as can be seen with the 6542, was cleverly elegant: the addition of a fourth hand, geared for one rotation every 24 hours, was the most complex modification required.

Being that a un-adjustable 24-hour hand was no use on its own, the bezel was also switched out for one with a 24-hour scale, divided into equal sections in red and blue to indicate the day and night. And you can see here that the original GMT-Master didn’t have a ceramic bezel like the modern one does—even though the ceramic material silicon nitride was actually discovered in the 50s—or the aluminium bezel other Rolex models had, but something else rather high tech.

Well, it was high tech back then, anyway—and I am of course talking about Bakelite. The forerunner to plastic, Bakelite was chosen for its ability to be moulded, which meant that luminous material could be formed into the bezel itself. It unfortunately turned out to be too fragile, and was replaced by the simpler aluminium bezel for the later 1675, but the idea was sound; the numbers in the bezel glowed, making the watch even more usable as pilots flew through the night—another simple yet brilliant solution.

To look at the modern GMT-Master today, as refined and as crisp as it is, could mislead you into thinking that it has always been a high priced, polished luxury item—but this couldn’t be further from the truth. Limited to the technology and budget available, the GMT-Master was as much an exercise in building the right watch for the job as it was about making do with the resources at hand. The 126710BLRO may seem a homage to a precision instrument built with no expense spared, but really the charm in the 6542 is that it is exactly the opposite.

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