Rolex. A Fine Stainless Steel Automatic Dual Time Wristwatch with Date, Center Seconds and "Tropical" Dial

With the beginning of transatlantic jet flights in 1956, travelers appreciated the fact journey times were reduced from 13 hours to 7, however they suffered from new phenomena, jet lag. Early airlines like Pan American worried about the possible effects of jet lag on their pilots and after research, the management advised them to keep on home time while overseas. Because crews needed to know the local and their home time, Pan Am and Rolex worked together to create a timepiece with an additional hour hand. The model was named GMT-Master after the world's standard time, Greenwich Mean Time. The watch further impresses with its attractive "tropical" dial.

Reference 6542 is illustrated in 100 Superlative Rolex Watches by J. Goldberger, 2008, p. 228