In the early 1950s the American airline Pan Am asked Rolex to develop a watch that could show the time in different time-zones simultaneously. This collaboration led to the creation of the GMT Master, a watch conceived from the start to be used by airline pilots travelling through different time zones.
GMT stands for Greenwich Mean Time (or Meridian Time), which has been the international time standard since 1884. It was chosen because the Prime Meridian (the line of 0° Longitude) runs through Greenwich.
Although Greenwich Mean Time (GMT) was replaced as the international time standard in 1972 by UTC (Coordinated Universal Time), Rolex kept the name GMT Master for their dual time-zone watch.
The first Rolex GMT Master, featuring the iconic red and blue bezel, was released in 1954 and is easily recognisable for the absence of crown guards.
Crown guards were introduced in 1959 and their shape was slightly pointed until 1965.
The bigger and thicker GMT Master II was released in 1983 and marked the introduction of sapphire crystals and white gold indices borders. Also from then on the 24 hour hand became independently adjustable.
An updated version of the Rolex GMT Master II released in 2006, featured a number of technical changes including a larger Triplock crown (from the diver's watches), which is more water resistant , more aesthetically pleasing and easier to use.
The new model also features several cosmetic changes, such as larger case, hands and hour markers and also a new bezel made with an extremely hard ceramic material that is more scratch and fade resistant. Also included in the update is a new and more luxurious style of bracelet that has heavier solid links and a machined clasp.
How do you set the Rolex GMT to show two time zones?
First you set the red arrowed "GMT" hand to track your home time zone by matching it to the corresponding hour on the 24 hour graduated rotating bezel. Next you set the hour hand to the time of the country where you are currently in. As you move between countries in different time zones, you can move the "standard" hour hand forwards or backwards to match the local time.