The Rolex GMT-Master origins
The Rolex GMT-Master story began in 1954 when Rolex introduced the reference 6542. The watch was housed in the classic steel Oyster case, which was 38mm in diameter. This was one of the first sports watches from Rolex and construction-wise, it set the standard for the foreseeable future. As with the present-day watches, the 6542 case was essentially of three-piece design.
The watch had two innovations that were big news at the time, but aspects we take for granted in the modern era. The first and less obvious was the date magnifying bubble, or to use Rolex terminology the cyclops. This was a new feature introduced the year before (1953) on the Datejust line. The second was, of course, the dual time zone complication.
The dual time zone was a useful tool for pilots and those who were travelling a lot across different continents. The ability to track local and home time was especially useful for commercial pilots. The American airline company, Pan American Airlines (or Pan Am for short) approached Rolex and asked them to develop a watch for their pilots. This partnership led to the development of the GMT-Master and in particular the first reference 6542. The commercially released watches housed a base caliber 1030 which was modified to include the 24 hour hand and was given the caliber number 1065. This chronometer rated movement was a four-hand calibre with date function. The 24 hour hand completed one full rotation every 24 hours and the bi-directional bezel could be rotated to allow the wearer to monitor the home time once they had adjusted their watch to local time or vice versa.
The iconic red and blue bezel made its debut on the 6542. Known to collectors as the ‘Pepsi’ bezel, due to its colour scheme being reminiscent of the well known cola brand, the blue half presents night hours (18:00 to 06:00) and the red half, day hours (06:00 to 18:00).
1960's
In 1959 Rolex launched their second series of the GMT-Master, a reference that would run until approximately 1980, the reference 1675. This new reference featured the new 1530 series movement, in the case of the GMT-Master caliber 1565. The most striking feature of the updated watch was the presence of crown guards. The case had been enlarged by 2mm and was now 40mm (excluding the crown guards) and was again available in both stainless steel (1675/0) and 18ct yellow gold (1675/8).
Rolex also introduced the aluminium insert as standard on the reference 1675. On the steel version the ‘Pepsi’ bezel was standard and on the yellow gold watch the insert was brown. The 1675 went through two crown guard versions too. The first iteration is referred to by collectors as pointed crown guards (PCG) or in Italian ‘cornino’. This was due to the thin and sharp profile of the guards. The later version is much thicker and rounded and can be referred to as rounded crown guards as per the lingo used for Submariners.