In the 1950's innovations in aviation technology made transatlantic travel a more appealing option than ever before. The airline Pan Am quickly emerged as a leader in transatlantic travel by jet plane. Due to the unprecedented success of the Rolex Sports models, the world's largest airline, Pan-Am, commissioned a watch which would enable their pilots to keep track of time in two locations.
With the help of Pan-Am's Captain Frederick Libby (a decorated World War II veteran and one of the airlines' most respected navigators), Rene-Paul Jeanneret conceived of a watch with an additional hour hand that revolved once every 24 hours and a rotatable 24-hour bezel. The GMT-Master was created.
Although the watch had been made to Pan-Am's requirements, many others came to depend on the watch; particularly military pilots who kept the rotating bezel at "12", thereby enabling the watch to give them both civilian and military (or 24 hour) time. Amongst the pilots who came to rely on the GMT Masters most were those chosen by NASA to fly the North American X 15.
Rolex perceived the GMT-Master almost solely as a pilot's watch. While the introduction of the Boeing 707 had caused Pan Am to commission the GMT Master, subsequently the people who flew on them as passengers became the main customers for the watch. With the introduction of jet travel, many people travelled between countries and hence between time zones. For these new international travellers the GMT Master was extremely useful.
IIn 1954, the first GMT Master, ref. 6542, was launched. This model was very distinctive,with Mercedes hands and an extra hour hand that was clearly differentiated by the triangle at the tip. Instead of the usual metal bezel insert, there was a special transparent acrylic insert, which had twenty-four hour markings printed on its underside. This material was chosen to cut down reflectivity and to enhance legibility by pilots. This acrylic bezel insert was the first item to be changed in 1956, giving way to a metal insert with the numbers now screenprinted. These new bezels were less likely to crack than the earlier plastic ones but were much more likely to fade in bright sunlight. The original plastic bezel inserts were luminous and it seems that the tritium used to paint them had somehow become contaminated with Strontium 90.
Once that problem was fixed, Rolex confirmed to its customers that the model was safe for use. The present watch includes a note from Rolex which states: ?It is hereby certified that the bezel and dial of this GMT Master No. 461831 have been tested and do not contain any substance in violation of the Atomic Energy Commission regulations."