Rolex produced specific models suitable for the extremes of deep-sea diving, caving, mountain climbing, polar exploration, and aviation. Early sports models included the Rolex Submariner (1953) and the Rolex Oyster Perpetual Date Sea Dweller. The latter watch has a helium release valve, co-invented with Swiss watchmaker Doxa, to release helium gas build-up during decompression. The Explorer (1953) and Explorer II (1971) were developed specifically for explorers who would navigate rough terrain, such as the world-famous Mount Everest expeditions. Another iconic model is the Rolex GMT Master (1954), originally developed at the request of Pan Am Airways to provide its crews with a dual time watch that could be used to display GMT (Greenwich Mean Time), which was the international time standard for aviation at that time and was needed for Astronavigation during longer flights. Rolex is the largest manufacturer of Swiss made certified chronometers. In 2005, more than half the annual production of COSC certified watches were Rolexes. To date, Rolex still holds the record for the most certified chronometer movements in the category of wristwatches. Rolex SA is owned by the private Hans Wilsdorf Foundation, which is registered as a charity and does not pay corporate income taxes. In 2011, a spokesman for Rolex declined to provide evidence regarding the amount of charitable donations made by the Wilsdorf Foundation. In Geneva, where it is based, it has gifted, among many things, two housing buildings to social institutions of Geneva. Rolex was also the second watch company to create a water resistant wristwatch that could withstand pressure to a depth of 330 feet (100 m). Wilsdorf even had a specially made Rolex watch (the watch was called the "DeepSea") attached to the side of Trieste, which went to the bottom of the Mariana Trench. The watch survived and tested as having kept perfect time during its descent and ascent. This was confirmed by a telegram sent to Rolex the following day saying "Am happy to confirm that even at 11,000 metres your watch is as precise as on the surface. Best regards, Jacques Piccard".
Although the first Rolex GMT Master watch was available only in stainless steel, as it was created as a functional work watch, Rolex has been making premium models in both mixed steel and gold, and all-gold since the 1950s, and there are even {special|exotic variations that incorporate creative styling that use gem stones. As I mentioned earlier, the Explorer II wears a little slimmer but is a touch wider than the GMT II, so which one you prefer comes down to personal preference and the kind of clothes you wear. If you tend to wear tighter fitting shirts and jackets, then you might find the GMT Master II more likely to get stuck on your cuffs. The most obvious difference between the watches is in the bezel. The Explorer II has a fixed bezel in brushed stainless steel and engraved 24-hour numerals painted black. The GMT Master II comes with a Cerachrom bezel and this, if you like the look of it, has some clear advantages. Ceracrom is a ceramic compound made and developed exclusively by Rolex. It’s almost entirely scratch-resistant and is unaffected by UV rays. It’s being used more and more by Rolex and features in the latest Submariner and the recently released Cosmograph Daytona. The numerals are etched into the bezel and then coated with a layer of platinum for maximum legibility and durability.
The Rolex GMT-Master wristwatch was originally designed in collaboration with Pan American Airways and issued by the airline to their crews on long-haul flights. ("GMT" in the name stands for Greenwich Mean Time also known as Coordinated Universal Time). The original GMT Master watch has a 24-hour display fourth hand complication directly linked to and displaying the same time zone as the standard 12-hour hand. This GMT hand enabled the crews to set the watch to GMT or another time zone, and, using the rotatable 24-hour scale bezel, set to the correct offset, a second time zone could be read. GMT or UTC is the time zone that is required for all aviation planning, weather forecasts, schedules and other paperwork. The GMT Master II works differently due to the bi-directional (i.e. it can be moved both ways) bezel. You can use it in the same way as above, but by turning the bezel you can track a 3rd time zone. Going back to the New York example; if we set the hour hand to east coast time (1 pm) and the 24-hour hand to GMT (6 pm) and we have, say, a colleague in Hong Kong that we need to contact on the business trip—Hong Kong is 8 hours ahead of GMT—simply turn the bezel eight clicks anti-clockwise and then read which number lines up with the 24-hour hand. Using our earlier example, it should read 2 am, but bear in mind this will be the following day compared to both the UK and New York.