Why the GMT-Master Still Makes the CaseThe goal was simple: give pilots a way to read two time zones simultaneously. The result was a 24-hour rotating bezel, color-coded in two blocks so the wearer could distinguish AM from PM at a glance, paired with an additional GMT hand that completed one rotation every 24 hours. Rolex developed the concept in collaboration with Pan American World Airways, which needed something pragmatic for its transatlantic crews flying long distances for the first time. The watch launched in 1955 and became the official watch of Pan Am.That functional premise is largely obsolete. Few, if any, are navigating by wristwatch in the cockpit of a modern airliner, and a smartphone handles dual time-zone reading without asking you to understand bezel mechanics. None of that has slowed the GMT-Master's market at all. In fact, quite the opposite! The GMT has been one of the best performing sports models in the Rolex catalog in the 21st century.