The Rolex GMT-Master, launched in 1955, was created for pilots needing to track two time zones.
Rolex developed the watch with Pan American World Airways for its crews, who needed to read local time and Greenwich Mean Time during long international flights. Its distinctive 24-hour hand works with a rotating 24-hour bezel to show the second zone.
The original model was the reference 6542, fitted with a bakelite bezel and a 24-hour scale. Later versions used more durable materials and eventually gained independently adjustable hour hands.
The GMT-Master is often confused with the GMT-Master II. The GMT-Master II arrived in 1983 and allows the 12-hour hand to be adjusted independently, making it more flexible when setting local time.