With Rolex fitted green presentation box.
The present GMT-Master is a very rare and early version of reference 6542. It's most important feature is the "double-red" writing on the dial, giving the depth rating 50m = 165ft and model name in red. Only very few, to the best of our knowledge less than a handful, references 6542 watches carry this charismatic double red writing. Interestingly, the depth rating and model name are held in different tones of red.
Reference 6542 can be distinctly characterized by featuring a bakelite bezel and the absence of crown-guards. Early GMT-Masters such as this one, still retaining its original bakelite bezel as well as the correct period Oyster bracelet and clasp stamped 2.55. are exceedingly rare finds. Examples furthermore blessed with private provenance and an ultra-rare dial version are the rarest sightings in this field.
For an example of a GMT Master ref. 6542 with double red writing see 100 Years of Rolex, 1908-2008 by Franca e Guido Mondani.
Due to the extraordinary success of the Rolex Sports models in the 1950s, it came as no surprise when the world's largest airline Pan Am commissioned a specially designed watch allowing their pilots to keep track of time in two locations.
With the beginning of transatlantic flights with jet aircrafts in 1956, travellers appreciated the fact that the journey times were reduced from 13 hours to 7 but suffered from new phenomena, jet lag. Worried about the possible effects on their pilots, and after research, Pan Am management advised them to keep on "home" time while away from base. As at the same time they needed to know the local time, a joint Pan Am and Rolex task force was assigned. The team devised a watch with an additional hour hand, which revolved once every 24 hours, and a rotating bezel marked with those same 24 hours. The model was named "G.M.T.-Master" after the world's standard time, the Greenwich Mean Time.
The first GMT model, reference 6542, was launched in 1954 and was immediately recognizable by the bright acrylic or bakelite bezel insert with the twenty-four hour markings printed on its underside. This material was chosen to reduce reflection which would disturb the pilots. The bezel ring was also made of acrylic and coated in an alloy to resemble metal. It then turned out that the flexibility of this material could cause the bezel insert to break and that in very warm environments the printing would often flake off. Consequently, Rolex decided to replace the acrylic insert against a more resistant metal version.