IIn the 1950s 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, that met the introduction the Rolex Sports models, it came as know surprise when the world's largest airline Pan-Am commissioned a watch to be designed which was specific to their needs, enabling their pilots to keep track of time in two locations. In conjunction with Pan-Am.'s Captain Frederick Libby (a decorated World War II veteran and one of the airlines most respected navigators), Rene-Paul Jeanneret devised the concept of a watch with an additional hour hand, which revolved once every 24 hours and a rotatable bezel marked with those same 24 hours, hence the GMT-Master was created.
Although the watch had been made to a Pan-Am requirement many other pilots 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, where those chosen by NASA to fly the North American X 15. Rolex perceived the GMT-Master almost solely as a pilots watch. Whilst it had been the introduction of the Boeing 707 that had caused Pan Am to commission the GMT Master, it was the people who flew on them as passengers who became the main customers for the watch. With the introduction of jet travel, many people were now travelling between countries and of course between time zones. For these new international travellers the GMT Master was the answer to their prayers. IIn 1954, the first GMT Master, ref. 6542, was launched. This model was very distinctive, it had Mercedes hands and an extra hour hand had been added which was clearly differentiated by the triangle at the tip. Instead of the usual metal bezel insert, there was a special insert of transparent acrylic which had twenty-four hour markings printed on its underside. This material was chosen to cut down reflectivity and avoid blinding the pilots. This acrylic bezel insert was the first item to be changed in 1956, giving way to a metal insert with the numbers now screen-printed. 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 the problem was fixed, Rolex made sure to confirm 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."