Rolex GMT Rolex launched the first GMT Master ref. 6542 in 1954, after a year of development. Considered by Rolex to be a pilot?s watch, the first GMT models featured a transparent acrylic bezel insert which had twenty-four hours markings printed on its underside. This material was chosen to avoid reflectivity that might blind a pilot. The bezel ring was also made of acrylic and was coated in an alloy to resemble metal. The original plastic, or Perspex, bezels were luminous and the tritium used to paint the numbers somehow became contaminated with Strontium 90. Once Rolex corrected the problem, 6542?s that were inspected and tested by Rolex were issued a note stating that the dial and bezel did not contain any unsafe substances. The flexibility of the acrylic bezels made them susceptible to cracking and by 1956 Rolex began changing acrylic bezels to metal bezels with screen-printed numbers. While these metal bezels were less likely to crack they were prone to fade with exposure to sunlight.
The GMT was an immediate success and was quickly adopted as the official timepiece of many leading airlines. In late 1960, the second GMT-Master was issued, ref. 1675. The GMT 1675 model was fitted with protective crown guards, the first models having pointed guards which later became rounded. Ref. 6542 was kept in production for a few years following the launch of the 1675, but after 1961 it was only available in 18K gold