The Rolex Caliber 3075
An unqualified triumph, even by the standards of the most successful watchmakers of all time, the Rolex GMT-Master series has long been the benchmark by which all other dual time zone watches are measured.
Starting life in the 1950s and developed in conjunction with Pan-Am Airways, the first of the breed, the ref. 6542, was in essence a modified version of the Turn-O-Graph, outfitted with a new movement and color scheme on the bezel; the distinctive blue and red two-tone which quickly earned the nickname the ‘Pepsi’.
During its now 60+ years in production, it has gone through some of the widest ranging changes and updates of any of the brand’s sports models. With enough variation between each reference, both major and minor, to satisfy even the most detail-oriented watch geek, the range has garnered a far-reaching and diverse fan base.
The ref. 16750 released in 1981 became only the third iteration of the original series, taking the baton from the long-running ref. 1675, the model which had secured the GMT’s world-beating reputation following its debut in 1959.
Stylistically very similar to its predecessor, the ref. 16750 actually marked the start of a new era for the ultimate pilot’s watch. It was the first of the breed to be fitted with one of Rolex’s 3000 series of calibers, a replacement for the hugely popular Cal. 1575GMT found in the older model.
The Cal. 3075
The GMT-Master’s new engine, the Cal. 3075, was built around the architecture of the family’s base movement, the Cal. 3035. It increased the balance speed from the 19,800bph of the Cal. 1575 and introduced the now standard high-beat 28,800bph—the eight ticks per second frequency that gives all Rolexes made since the characteristic smoothly sweeping seconds hand.
Alongside the uprated speed, the 3075 also brought the Quickset date function to the GMT for the first time. A logical improvement for a luxury traveller’s watch, it meant wearers were able to advance the date directly via the crown in its second position, rather than having to wind the center hands through 24 hours. It might seem like a somewhat trivial upgrade, but Rolex’s unassailable reputation has been built on their almost constant striving to improve their customer’s experiences with their products in any way possible, no matter how small.
Besides those two important changes, many of the elements that had worked so well for the retiring Cal. 1575 were carried over onto its successor. The 3075 retained the all-important hacking feature that stopped the seconds hand while setting the time, as well as the trademark Rolex setup of free sprung balance with a Breguet overcoil, regulated by their own Microstella system—four gold screws on the inner rim of the balance wheel that allow for the minutest adjustment to its timing, offering a far higher level of precision than using a traditional regulated balance.
Swapping to a fast rotating barrel helped up the 3075’s power reserve to 50 hours from the previous 48, as well as improving the stability of the drive train.
Physically, there’s practically nothing to choose between the old and the new. The 3075 loses a shave in height, going from 6.3mm to 6.2mm, and it gains a couple of extra jewels to deal with the Quickset function, taking it up to 27.
Other than that, the winning formula Rolex had come up with for their 1500 range of movements continued to set the standard for mechanical calibers in the 3000 series. Purists will argue all day over which is the better of the two, but both remain among the most accurate and reliable mechanisms ever made, and their robust simplicity make them particular favorites of fine watch repairers.
The Difficult Third Album
Furnished with a shiny, all-new movement or not, the ref. 16750 was a particularly short-lived reference in the GMT-Master story. Only in production for seven years, it was very much a transitional model—a placeholder while Rolex set about developing a caliber that could deliver the final prerequisite for a true multi-time zone watch.
It wasn’t until 1988 and the arrival of the first of the GMT-Master IIs, the ref. 16760, that the definitive globetrotter’s companion gained a GMT hand that could be adjusted independently of the hour hand. With that vital addition, for which, ironically, Rolex had to sacrifice the only recently introduced Quickset date feature, travellers could now set a second time zone instantly, as well as keep track of a third via the engraved bezel.
As any Rolex enthusiast knows, a brief production run very often equates to a future classic, especially if it concerns one of the crown’s most beloved names. The ref. 16750 is one such watch.
Although something of a blink-and-you’ll-miss-it reference, it underwent a number of styling alterations during its life, which can add significant premiums to the price of vintage models.
The earliest pieces were released in stainless steel with a matte black dial, while towards the end of its run, it swapped to glossy dials and included hour markers picked out in white gold. Finding a ref. 16750 with its original matte face still intact is no easy task, principally because Rolex would often replace them for gilt during routine servicing. It is this rarity that makes them the most highly sought after on the pre-owned market.
It also came available with a choice of bezel; the iconic Pepsi blue and red or with an all black surround that bore more than a passing resemblance to the Submariner.
As well as the workmanlike steel model, Rolex launched precious metal versions of the watch, with an all yellow gold ref. 16758 and a Rolesor ref. 16753. These more luxurious variants had their own notable quirks; the steel and gold piece carried on its two-tone theme with the ‘root beer’ bezel option, a brown and cream surround that made for an interesting alternative to the timeless original.
And the yellow gold ref. 16758 could be had with a Serti dial—a Rolex term taken from the French word ‘sertir’ meaning ‘to set’. It refers to those pieces with gemstones such as diamonds, rubies or sapphires used on the hour markers at 6, 9 and 12 o’clock, completing the GMT-Master’s transformation from tool watch to status symbol.
Intriguingly, it was only this solid gold example that was ever fitted with the newly developed sapphire crystal that was making its way on to the Submariner and Sea-Dweller of the same era. The steel and Rolesor versions had to make do with the traditional acrylic covering.
A One-Watch Movement
The Cal. 3075 was in service for just a brief instant in the Rolex saga. It brought the high-beat movement, with its inherent increase in accuracy and resilience, to one of the most popular of the brand’s professional range.
Building on the exceptional Cal. 1575, it added both extra precision and a new level of convenience, keeping the GMT-Master as the standard bearer for the travelling elite.
— Featured and Body Photo Credits: BeckerTime’s Archive.