In 1953 Pan Am Airlines approached Rolex with a request for a watch that could show the time simultaneously in two different time zones.
A year later and reference 6542 GMT Master was born with a rotating 24hr bezel, GMT hand and cyclops date window.
Unlike the rotating bezel of the Submariner, the GMT Master bezel was made from Bakelite – the first synthetic plastic – as was the bezel ring which was coated to resemble metal. The insert was transparent with the blue and red sectors printed on the reverse.