Produced wristwatch showing two time zones

The Rolex GMT Master, reference 6542, was introduced as a wristwatch capable of displaying two time zones simultaneously. This innovation catered primarily to the needs of pilots and frequent travelers, allowing them to keep track of time in different regions without the need for multiple watches. The GMT Master featured a rotating bezel that enabled users to easily adjust the second time zone, enhancing its practicality for those who crossed time zones regularly. While the GMT Master is often credited with popularizing the dual-time zone concept, it is important to note that Longines had previously developed the DualTime model, which was introduced 25 years earlier. This earlier model also allowed users to read two time zones, demonstrating that the idea was not entirely new when Rolex launched its version. The introduction of the GMT Master marked a significant advancement in wristwatch functionality, appealing to a growing market of international travelers and aviation professionals who required precise timekeeping across different locations.