From the various tests carried out in the 1940s, it emerged that one of the methods of counteracting jet lag was to possess an instrument that would simultaneously indicate both the time zone of the place of departure and that of the flight's destination.Pan-Am, the former U.S. flag carrier, was among the first to meet this need, entrusting Rolex with the creation of a watch equipped with the specifications needed by pilots. Rolex then introduced the GMT Master model, equipped with a rotating bakelite bezel and a hand to mark the dual time zone. In the late 1950s and early 1960s, it was realized that the radioactive material that was used in making the GMT's luminous bezel was dangerous. The Maison therefore issued an announcement inviting owners of this model to return the watch to the parent company in order to replace the radioactive bakelite bezel with a metal one. The fragility of the old bezel, combined with this replacement action carried out by the Maison itself, has meant that very few examples, such as the one we propose, still have the original bakelite bezel.