A precise and reliable wrist watch with GMT/second time-zone function is a must have accessory for both international travelers and aviation professionals who frequently pass through various time-zones around the globe. These time-instruments are also helpful for all those who regularly maintain overseas contacts in their professional or personal life.

GMT refers to Greenwich Mean Time, the mean solar time at the Royal Observatory in Greenwich, London. Initially used by the British mariners, and then by Railways and telegraph operators, GMT was accepted worldwide as the standard time independent of location.

Since 1963, GMT has been replaced by Coordinated Universal Time (UTC), which is more accurate and precise time measurement, as the primary time standard by which the world regulates clocks and time. Still, most people use the term GMT for finding the corresponding time in a different time-zone.

Post WW-II, commercial passenger airliners began operating long-haul flights. In the beginnings, both aviation professionals and frequent travelers had faced difficulties to calculate the local time of their destination located in a different time-zone. So, there was a need to develop timepieces that can indicate two time-zones simultaneously: Local time and reference/home time.

To meet the specific needs of aviation professionals, Rolex developed the Oyster Perpetual GMT-Master, which displayed two different time zones simultaneously. Launched in 1955, this new robust and functional watch became the official watch of several airlines including the famous Pan American (Pan Am) World Airways.

The GMT-Master was used for navigation by the crew on the first non-stop intercontinental flight between New York and Moscow in 1959. When the supersonic passenger jet Concorde made its final series of test flights at the end of the 1960s, its pilots were wearing GMT-Master watches.

Rolex GMT-Master

The GMT-Master family, which represents the first generation Rolex GMT watches, includes various models released from 1955 to 1988.

In 1954, Rolex developed Caliber 1036, the first GMT movement from the brand. This 25-jewel, 18,000 vph, self-winding caliber features hour, minutes, date and an additional GMT hand. This movement became the foundation stone for GMT-Master watches. All of these timepieces also featured a rotatable 24-hour bezel and an additional hour-hand for indicating reference time (GMT).

The very first GMT-Master model (Ref. 6542) created for Pan Am crew featured a 38mm diameter Oyster-steel case and the famous ‘Pepsi’ bezel. Made from Bakelite (Plexiglas), the bezel insert featured the colours, numerals and graduations painted on the reverse.

The bezel insert was divided into two halves – one red, to correspond with daylight hours, and one blue, for night-time hours. Over the years, the 24-hour graduated insert has been made available in a range of other colours. The GMT-Master Ref. 6542 offered a water resistance up to 50 meters.

The GMT-Master watch family continued to expand its product range by adopting newly inducted calibers and also by releasing new variants featuring different materials (steel, steel and gold or gold); case sizes (38mm to 40mm) and bezel combinations (Bi-color or single color). The references that followed Ref. 6542 are Ref. 1675, Ref.16750 and Ref. 16700.

Introduced in 1959, the GMT-Master Ref. 1675 came with Caliber 1565, a self-winding GMT movement with 26 jewels, 18000 vph and 42 hours power reserve.

In 1965, Rolex started equipping the new Ref. 1675 production models with Caliber 1575 GMT, a 25 jewels self-winding movement that beats at 19,800 vph. It has a power reserve of approximately 44 hours. The Ref. 1675 has a water resistance of 50 meters.

The other two noteworthy references from this generation are Ref. 1675/8 (gold case) and Ref. 1675/3 (yellow Rolesor case with steel and yellow gold).

The GMT-Master Ref. 1675/3 was available in two configurations: a black dial version with black bezel and a brown dial version with brown bezel. Followed by these versions, Rolex also introduced a new version of Ref. 1675/3 featuring brown dial and a bi-color bezel in brown and golden shade. Rolex lovers usually refer the GMT watches with brown dial/ brown bezel as Root Beers.

In 1981, Rolex introduced the GMT-Master Ref.16750, which featured Caliber 3075, a high-beat self-winding movement endowed with quick-set date function. Beats at 28,800 vph, this 27-jewel movement and has a power reserve of approximately 50 hours.

Introduced in 1989, the Ref.16700 was the last model released from the GMT-Master family. This model houses Caliber 3175. This 31-jewels, 28,800 vph self-winding movement has a power reserve of approximately 48 hours.

At the same time, Rolex also updated GMT-Master’s bezel inserts with new materials. For example, initial production models featured Bakelite bezels with radium-based luminous markings. As the Bakelite is easily breakable, the brand introduced aluminum bezel inserts. In the 1960s, following a lawsuit regarding the radiation hazards of radium, Rolex recalled the radium-applied bezel inserts and replaced them with anodized aluminum bezel inserts without any luminous application. In 1963, Rolex began using Tritium as the luminescent material for their watches.

In 1998, they switched over from Tritium to Luminova. In 2007, Rolex introduced watch models with Superluminova.

Further, except a few variants, most of the GMT-Master models featured bi-color bezel inserts to distinguish between day and night times. The dual coloring of aluminum bezel inserts were achieved by a special anodizing process.

Rolex GMT-Master II

The GMT-hand of all watch models from the GMT-Master family is coupled with the hour-hand. When you adjust the hour-hand, the GMT hand also rotates and aligns to the reference time (GMT/UTC). To track an additional time-zone, the wearer has to rotate the bezel.

In 1982, Rolex introduced a new movement that allowed the hour hand to be set independently of the other hands. To clearly mark this remarkable progress, and to avoid any mix-up with the GMT-Master, the model fitted with the new type of movement was named the GMT Master II.

In the gmt master ii models, the GMT hand is independent from the other hands. The wearer can align this hand to any preferred time-zone, and it will continue to track a reference time-zone or an additional time-zone without taking any reference from the hour hand or the rotating bezel. Additionally, the wearer can also track a third time-zone by rotating the bezel.

The first model from the GMT-Master II series is Ref. 16760 aka Fat Lady. Equipped with the newly inducted self-winding Caliber 3085, this 40mm diameter Oyster steel version features a ‘Coke’ bezel featuring a black and red colored insert. It was also the first Rolex GMT Oyster steel watch to be fitted with sapphire crystal glass. This model used tritium tubes for luminescence. Production period from 1983 to 1988.

Introduced in 1989, the Ref. 16710 was the second release from the GMT-Master II family. It featured a 40mm diameter Oyster steel case and houses the self-winding Caliber 3185. Some models released in the last production batches feature Caliber 3186. This reference was made available with Pepsi (Blue& Red), Coke (Black & Red) and All-Black bezel versions. Anodized aluminium inserts. Rolex produced this model till 2007.

The Ref. 16710 models produced from 1989 to 1997 featured tritium tubes as light source. The models produced from 1998 to 2000 featured Luminova and those produced from 2000 to 2007 featured SuperLuminova. Some notable variants from this generation are Ref. 16713 (steel/yellow gold) and Ref. 16718 (yellow gold).

GMT Master-II models with Caliber 3186 & Ceramic Bezel Inserts

In 2005, Rolex developed Cerachrom bezel insert to replace the aluminum bezel inserts used with GMT and diving watches. Patented by Rolex, the Cerachrom insert is made of an extremely hard and corrosion-resistant ceramic. It is virtually scratchproof, and its colours are unaffected by ultraviolet rays. The moulded, recessed numerals and graduations are coated with gold or platinum using a PVD process.

In 2005, Rolex unveiled its first watch with a ceramic insert: an Oyster Perpetual GMT-Master II in 18 ct yellow gold with a bidirectional rotatable bezel and a 24-hour graduated insert in black ceramic (Ref. 116718 LN).

In 2006, the brand introduced a steel/yellow gold version with black ceramic bezel insert (Ref. 116713LN).

In 2007, Rolex launched an Oyster steel version with black ceramic bezel insert (Ref. 116710 LN). In the same year, Rolex registered the trademark “Cerachrom”. The brand’s ceramic components are now known as the “Cerachrom bezel” and the “Cerachrom insert”.

Rolex also released a blue ceramic and green ceramic inserts for other collections: In 2007, a blue ceramic insert was introduced on the new generation Oyster Perpetual Yacht-Master II model. In 2010, green ceramic appeared on an Oyster Perpetual Submariner Date for the first time.

Initially, Cerachrom bezel inserts were made available only in single colors like black, blue and green. It took another three years of research and development to create a bi-color Cerachrom bezel insert.

In 2013, Rolex introduced its first single-piece, two-colour ceramic bezel insert – blue on one half and black on the other – on an Oystersteel version of the GMT-Master II (Reference 116710BLNR). This GMT-Master II model featuring blue and black ceramic bezel is known as Batman.

In 2014, Rolex unveiled the two-colour bezel insert in red and blue ceramic, on a GMT-Master II in 18 ct white gold (Ref. 116719BLRO).

GMT-Master II models with Cal. 3285 and Ceramic bezel insert

In 2018, Rolex released its new generation GMT-Master II models equipped with Cal. 3285, a self-winding mechanical movement entirely developed and manufactured in-house.

This state-of-the-art mechanical caliber incorporates a number of Rolex innovations like optimized Paramagnetic blue Parachrom hairspring, Large balance wheel with variable inertia, Rolex overcoil, Perpetual rotor, High-precision regulating via four gold Microstella nuts, Traversing balance bridge, High-performance Paraflex shock absorbers and the Chronergy escapement enhanced with Paramagnetic features and increased autonomy.

It has 31 jewels and beats at 28,800 vph. This movement provides an impressive power reserve of approximately 70 hours.

At Basel-world 2018, Rolex released Reference 126710 BLRO, a new edition of Oystersteel GMT-Master II featuring a bi-color Cerachrom bezel insert in the iconic Pepsi (blue and red) configuration.

Along with this much awaited model, the brand also presented a two-colour bezel insert in brown and black ceramic, on two variants of the GMT-Master II: one in 18 ct Everose gold (Ref. 126715 CHNR) and the other in an Everose Rolesor version (Ref. 126711 CHNR).

In 2019, Rolex introduced a new version of the Oystersteel GMT-Master II featuring two-colour Cerachrom bezel insert in blue and black ceramic (Ref. 126710 BLNR). This model is known as Batgirl.

The GMT-Master II’s Oyster case guarantees waterproof to a depth of 100 metres (330 feet). The middle case is crafted from a solid block of corrosion-resistant Oystersteel or 18 ct gold. The case back, edged with fine fluting, is hermetically screwed down with a special tool that allows only certified Rolex watchmakers to access the movement.

The winding crown, fitted with the Triplock triple water-proofness system, screws down securely against the case. The crown guard is an integral part of the middle case. The crystal, with a Cyclops lens at 3 o’clock for easy reading of the date, is made of virtually scratchproof sapphire.

Rolex offers a three-piece link Oyster bracelet for the Everose Rolesor version and versions in 18 ct white gold or 18 ct Everose gold. The versions in Oystersteel feature a five-piece link Jubilee bracelet. These bracelets are equipped with a Rolex designed and patented Oysterlock safety clasp that prevents accidental opening.

They are additionally fitted with the Easylink comfort extension link, developed by the brand, which allows the wearer to easily increase the bracelet length by approximately 5 mm, providing additional comfort in any circumstance. A concealed attachment system ensures seamless visual continuity between the bracelet and case. On the 18 ct gold versions of the GMT-Master II, the Oyster bracelet includes ceramic inserts inside the links to enhance its flexibility and longevity.

Like all Rolex watches, the GMT-Master II is certified as a Superlative Chronometer. This certification involves two phases of testing.

Firstly, COSC (Swiss Official Chronometer Testing Institute) tests the precision of every Rolex movement and issues the official chronometer certificate. Each of these COSC certified movements is tested again by Rolex after being cased, to ensure that it meets criteria for a specified precision rating that is superior than those for an official chronometer.

The tolerance for the average rate of a Rolex Superlative Chronometer is of the order of −2/+2 seconds per day. The Superlative Chronometer status is symbolized by the green seal that comes with every Rolex watch and is coupled with an international five-year guarantee.

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