Based in Geneva, Tudor watches is a sub-brand of Rolex, originally registered in 1926 by Hans Wilsdorf, who is best known for founding Rolex SA. In the beginning, Tudor was positioned to be a more affordable alternative to Rolex watches. Today, Tudor and Rolex are sister companies, both owned by the Hans Wilsdorf Foundation. In 1954, Tudor’s Oyster Prince Submariner was introduced. This tool watch continuously evolved to meet the needs of divers over the years. During the decades between the 1960s and 1980, there were several navies issuing Tudor Submariners to divers, including the elite SEALs of the U.S. Navy, and the Marine Nationale, or French Navy. From 1969 to 1999, over 20 different Tudor Submariner references were produced. In 2015, Tudor released their first in-house caliber, MT5621, a self-winding caliber with a bidirectional rotor system.