Rolex | Submariner, Reference 5512, A stainless steel wristwatch with bracelet, Circa 1961 | 勞力士 | Submariner 型號5512 精鋼鏈帶腕錶，約1961年製

First introduced in 1959, the Submariner reference 5512 was discontinued 20 years later. This new reference launched several notable changes to the Submariner. Firstly, the case size increased to 40 mm and for the very first time, Rolex introduced crown guards to protect the crowns. The current watch made in 1961 is fitted with a later gilt service dial that can be determined by the 'Swiss T<25' designation at 6 o'clock, which Rolex introduced in 1965 to confirm the use of tritium for the indexes.