In 1954 Tudor created the Reference 7922, their first professional divers’ wristwatch. This example, part of the early series, features its reference and serial number on the caseback and is fitted with its correct 100m=330ft dial and its correct 6 mm crown. Still reacting strongly to the Geiger counter, these historical examples were only produced during a short period before being replaced by reference 7924 in 1958 featuring a larger 8 mm crown and a 200m dial.