How to Use the GMT Function on the Rolex GMT-Master 1675, 16750 and 16710

The Rolex GMT-Master is the rare wristwatch built around a hand that is supposed to look wrong, a slender arrow that circles the dial once every twenty-four hours rather than once every twelve. That fourth hand, paired with a bezel marked out to a full day, is the entire point of the watch, and it is also the source of more confusion than almost any other Rolex complication. Owners regularly strap on a 1675, a 16750 or a 16710 and discover that the second time zone does not behave the way they expected it to.

The reason is simple and rarely explained well. Across these three references, Rolex quietly changed the way the GMT function actually works. The 1675 and the 16750 operate one way. The 16710 operates another. Knowing which watch is on your wrist determines exactly how you set it, and understanding the difference turns a puzzling extra hand into one of the most genuinely useful tools Rolex has ever fitted to a sports watch. This guide covers the history behind the complication and then walks through the correct method for each reference.

A Watch Built for the Jet Age

The GMT-Master owes its existence to a specific commercial problem. In the early 1950s, Pan American World Airways was opening long intercontinental routes that crossed several time zones in a single flight, and its crews needed a dependable way to keep track of time at home, time at the destination and the standardised reference time used in aviation. Pan Am approached Rolex, and the answer, introduced in the mid-1950s, was a watch that displayed two time zones at once.

The first GMT-Master, reference 6542, set the template that every later model would follow. A fourth hand swept the dial once every twenty-four hours, and a bezel divided into twenty-four hours let the wearer read a second zone against it. The bezel's two-tone red and blue colouring, the scheme later nicknamed Pepsi, was not decorative. It split the twenty-four-hour scale into daytime and night-time halves, so a pilot could tell at a glance whether it was noon or midnight in the zone being tracked. The earliest bezel inserts were made from a brittle plastic that proved fragile in service and was soon replaced with metal, but the principle was settled from the start.

Reference 1675 arrived in 1959 and ran for roughly two decades, and it is the model that fixed the GMT-Master in the popular imagination. It added crown guards flanking the winding crown, grew slightly in presence, and was produced across a long enough span to show real evolution in its dials and finishing. Early examples used the calibre 1565, replaced around the middle of the 1960s by the calibre 1575, which later gained a hacking seconds function around 1971. Neither movement offered a quickset date, so the date could only be advanced by running the hands through midnight. Most important for how the watch is used, the fourth hand on the 1675 was mechanically tied to the main hour hand, a detail that defines the entire first generation.

Understanding the Two Working Parts

Before setting any GMT-Master, it helps to understand what the two key components actually do. The complication stops being intimidating once the roles are clear.

The Twenty-Four-Hour Hand

The extra hand, usually tipped with a coloured arrow, rotates once per day rather than once every twelve hours. On a normal watch the hour hand passes each number twice a day, which makes it impossible to tell morning from evening without context. A hand that travels around only once in twenty-four hours removes that ambiguity. Read against a twenty-four-hour scale, it points to a single, unmistakable hour of the day, which is exactly what someone tracking a distant time zone needs. Whether that hand shows your home time or a second zone depends entirely on the reference, as the following sections explain.

The Rotating Bezel

The bezel is graduated from one to twenty-four and turns in both directions on all three references covered here. Its job is to act as a movable reference scale. By rotating it, the wearer changes the relationship between the twenty-four-hour hand and the numbers it points to, and that offset is how an additional zone is read. On the earliest and the latest of these GMT-Masters alike, the bezel is the difference between tracking one extra zone and tracking two.

The Coupled Generation: References 1675 and 16750

The 1675 and its successor, the 16750, share the defining trait of the original GMT-Master. Their twenty-four-hour hand cannot be set on its own. It is linked directly to the twelve-hour hand, so the two always move together in a fixed relationship. When you pull the crown and turn the hands to set the time, both advance in lockstep, and there is no way to separate them.

The 16750, produced through the 1980s, modernised the line without changing this behaviour. Its calibre 3075 introduced the quickset date, letting the date change independently of the hands through an intermediate crown position, and it ran at a higher frequency than the calibres before it. Some later examples also moved to a sapphire crystal. For all those improvements, the 16750 remained a GMT-Master of the original type. The hour hand and the twenty-four-hour hand stayed coupled, which is why a 1675 and a 16750 are set in precisely the same way.

Setting a Second Time Zone

Because the two hands cannot be separated, the bezel does the work of displaying the second zone. The method is straightforward. First, set the twelve-hour hand to your local time in the usual way, which automatically places the twenty-four-hour hand at the matching point on a twenty-four-hour scale. With the bezel triangle aligned to its neutral position at twelve o'clock, the fourth hand now indicates local time in twenty-four-hour form.

To track a second zone, count how many hours that zone sits ahead of or behind your local time, then rotate the bezel by that many hours. The twenty-four-hour hand now reads the second zone directly against the bezel scale. If the zone is two hours ahead, turn the bezel so its scale shifts two hours in the appropriate direction, and the arrow points to the correct hour in that distant city. The trade-off is that whenever you reset local time, such as on landing somewhere new, the relationship resets too, and you re-establish the second zone simply by rotating the bezel again.

A practical example makes it concrete. Suppose the owner of a 16750 in Sydney wants to keep an eye on Singapore, which sits two hours behind. With local Sydney time set on the main hands and the bezel in its neutral position, the wearer rotates the bezel to reflect that two-hour difference. The twenty-four-hour hand, unchanged, now points to Singapore time on the bezel. Local time is still read conventionally from the twelve and minute hands, and the second zone is read from the arrow against the bezel. The same sequence applies to a 1675, with the only practical difference being that the 1675 lacks the quickset date and must have its date advanced through the hands.

The Independent Generation: Reference 16710

The 16710 belongs to a different branch of the family, the GMT-Master II, and it solves the limitation of the coupled design. The breakthrough did not actually arrive with the 16710 itself but with reference 16760, the first GMT-Master II, introduced in the early 1980s and nicknamed the Fat Lady for the thicker case its new movement demanded. That movement, the calibre 3085, finally uncoupled the two hands. The twelve-hour hand could now jump forward or backward in one-hour increments, set through the crown, without stopping the watch or disturbing the twenty-four-hour hand.

The 16710 carried this capability forward in a slimmer, more elegant case from 1989 until 2007. Early examples used the calibre 3185 and later ones the calibre 3186, both offering the independent jumping hour hand alongside a quickset date and hacking seconds. It was offered with the red and blue Pepsi bezel, the all-black bezel and the red and black Coke bezel, the last of which had first appeared on the Fat Lady.

Tracking Three Time Zones

The independent hour hand changes the whole method and, just as importantly, lets the 16710 display three time zones rather than two. The approach is the reverse of the older watches in one key respect. Here the twenty-four-hour hand and the bezel hold a fixed reference, while the twelve-hour hand becomes the flexible, everyday display.

To set it up, begin by setting the twenty-four-hour hand to your home time, the zone you always want to keep, by adjusting the hands with the bezel in its neutral position. Then use the independent setting to jump the twelve-hour hand to your current local time. Because the hour hand moves on its own, you can advance or retreat it through the zones you cross without ever touching the twenty-four-hour hand, which continues faithfully showing home. The twelve and minute hands now display local time, and the fourth hand displays home time. If you want a third zone, rotate the bezel by the appropriate offset, and the twenty-four-hour hand will indicate that third zone against the bezel scale.

Consider the owner of a 16710 who lives in Sydney and travels to London. Before leaving, the twenty-four-hour hand is set to Sydney time, the home reference. On arrival in London, rather than resetting the whole watch, the traveller simply jumps the twelve-hour hand back to London local time in single-hour steps. The minute hand and seconds are left untouched, so timekeeping accuracy is preserved through the journey. The watch now shows London on the main hands and Sydney on the fourth hand, while the bezel remains free to track a third city if required. This is the flyer's GMT in its purest form, and it is the reason the 16710 is so often described as a true travel watch.

Why the Difference Matters

The distinction between the two generations is not really a question of one being better engineered than the other in every sense, but of how each is meant to be lived with. The 1675 and 16750 reward a wearer who keeps a steady local time and occasionally checks a single second zone, using the bezel as the adjustable element. The 16710 suits someone who genuinely moves between zones and wants to change local time instantly while a home reference stays fixed, then keep a third zone on the bezel for good measure.

It is worth clearing up the most common misunderstanding while it is in front of us. The headline upgrade of the 16750 was the quickset date, not an independent hand. Despite its more modern movement, it operates exactly like the 1675, and treating it as though it were a GMT-Master II leads only to frustration. The independent hour hand is the dividing line, and among the references covered here, only the 16710 has it.

Final Thoughts

The GMT-Master has carried the same essential idea for seventy years, a fourth hand and a twenty-four-hour bezel working together to compress the globe onto a single dial. What changed across the 1675, the 16750 and the 16710 was not the idea but the mechanism behind it, and that change is the entire reason these watches feel so different to operate. Set a coupled-hand 1675 or 16750 by fixing local time and letting the bezel carry the second zone. Set an independent-hand 16710 by anchoring home on the fourth hand and jumping the local hand as you travel. Understand which one you are holding, and the hand that was built to look wrong starts to make perfect sense.

References

1.    Rolex, GMT-Master II, Official Brand History and Specifications, rolex.com.

2.    BeckerTime, “What's the Difference: The Rolex GMT-Master vs the Rolex GMT-Master II,” beckertime.com.

3.    WatchGuys, “Rolex GMT-Master Buyer's Guide: History, References and Movements,” watchguys.com.

4.    Exquisite Timepieces, “Rolex 16700 vs 16710: Which GMT-Master Is Right for You,” exquisitetimepieces.com.

5.    GMT Forum, “GMT Movements and Hand Differences: 1675, 16750, 16700, 16760 and 16710,” gmtforum.com.

6.    Chrono-Shop, “Rolex Watch Cases Comparisons: GMT 1675, 16760, 16710,” chrono-shop.net.

7.    Hodinkee and Fratello Watches, reference and historical coverage of the Rolex GMT-Master and GMT-Master II references