LIP Blancpain watches were not the first dive watches on the market when they were introduced in 1953. They were, however, the most modern dive wristwatches at that time. The reliability and compactness of Fifty Fathoms models, which were originally designed for military use, became legendary. The reputation earned them the right to be used by armies such as French Navy, Czech, Polish, German federal, some Nordic countries, and also by the US Navy (SEAL, under water demolition team, Frogman).
This is a Blancpain LIP Fifty Fathoms circa 1950s. The dial does not say "Blancpain" and/or "Fifty Fathoms" - instead it is signed just "LIP." This is different from almost every other Fifty Fathoms watch I've seen; they are typically signed with one name or both. Less markings on the dial not only results in a cleaner look - it also means is more rare than a typical circa 1950s Fifty Fathoms.