Rolex’s sister company has been producing Submariners since the 1950s, and since that time, militaries across the world have been ordering them for issue to their sailors and soldiers. If you’re looking for a Tudor “mil-Sub,” as they’re often called, you should be prepared to spend a pretty penny — at this point, several tens of thousands of dollars, especially for “snowflake” versions. The most popular such issued Tudor watches are to the Marine Nationale, the French navy, with casebacks inscribed “M.N.” But other navies took delivery of Tudor dive watches as well, such as those of South Africa, Israel, and the U.S. (The British, rather famously, used Rolex, Omega, and C.W.C. watches.) While timepieces such as these sometimes come up for sale through conventional channels, you’ll often have to source them through a dealer, or even go through an auction house.