Thus debuted the first Rolex GMT- Master model, entering the scene in the mid-1950s as the first watch capable of simultaneously and perfectly legible display of two time zones.

Following the adoption of the new Boeing jets, capable of non-stop intercontinental flights, Pan-Am Airlines was faced with an inconvenience, which had never occurred at the time, but is now known as jet-lag.

The pilots and crew arrived at their destination so tired and confused from crossing several time zones in a 'relatively' short time span that the airline was persuaded to commission studies on this particular phenomenon, to the point of highlighting the benefit crew members derived from knowing the local time of arrival and time of departure at the same time.

Hence the idea of finding a watch suitable for the purpose. Thus was born a close collaboration between Pan-Am and Rolex which, after a year of joint research, led to the creation of the GMT-Master in 1954 and the first model identified with Ref. 6542. This GMT features a three-body Oyster case, water-resistant to a depth of 50 metres, a lacquered black dial and a continuous minute track, with a rotating bezel similar to the Submariner and Turn-O-Graph models.

The display of the second time zone is made possible thanks to the additional sphere that makes one complete revolution in 24 hours, indicating the time on the specific graduated bezel from 0 to 24. The latter, which can be rotated according to the time zone one wishes to display, flanks the classic time reading on the dial and is the distinctive element par excellence of the GMT-Master 6542.

The bidirectional rotating bezel, made of transparent bakelite, presents the 24-hour indication on a disc divided into two colours: red for the daytime hours, blue for the night-time hours.

Despite its great aesthetic impact, the bakelite bezel was fragile and excessively susceptible to breakage: to remedy the problem, Rolex decided to replace it with an aluminium insert that was much more resistant and capable of maintaining the graduation and colours unaltered. Over the years, a "legend" was nurtured that saw several examples, intended for the crews of each aircraft, being requisitioned by the managers. Until the day the head of Pan-Am noticed one on the wrist of an executive: he was not pleased and ordered that all the requisitioned watches be returned to the crews.

Juan Trippe, the head of the company, in order to avoid the discontent of the executives who felt sidelined, commissioned Rolex to produce a new version for them, made in no more than a hundred examples and distinguished by a white dial. These turn out to be the last examples produced with the reference 6542, to date considered the rarest version ever.