Rolex Submariner:

 In 1953 Rolex underwent stringent experiments, testing the Submariner prototype in deep waters to a depth of 3,150 meters (10,336 ft). The watch withstood the hardest tests, having survived sub-zero temperatures, as well as the wear and tear of expeditions. Rolex launched the Submariner (model 6204) at the Basel Fair in 1954 although it is believed that it was actually released in late 1953 and was based on the Rolex Explorer. On the contrary, the name "Submariner" was not officially patented until around 1960. When introduced, the Submariner was powered by the A296 movement but was then replaced with the 1030 movement and Mercedes hands, which is more elongated than the modern day version. In 1955, model 6538 replaced 6204, and the 6205 by 6536 respectively. Model 6536 then became 6536/1, featuring a chronometer version of the 1030 movement. New Submariner models featured a new scratch-resistant sapphire crystal and an upgraded depth rating of 1,000 feet.