The reference 5513 became the first Rolex for many years to become an official British Military issue watch, when it was issued to the divers of the Royal Navy in 1965. The military wanted certain modifications; in this case the modifications were so major as to almost be a new watch. First they wanted a new dial featuring a large 'T' in a circle under the center post. The high visibility hands were much larger and of a completely different shape. The hour hand was diamond shaped, while the minute hand was much wider than on a conventional Submariner and the seconds had had a unique diamond luminous indicator at the tip. Even the case was different from a standard Submariner. On the military models the spring bars were replaced with solid steel bars welded into the spring bar holes. The case was then polished so the hole was hardly visible. The rear of the case was then engraved with all the military specifications and issued numbers which enabled the quartermaster to identify the watch. At the end of the 1960s, another branch of the British Military, the Royal Marines ordered Submariners for their frogmen. These were even more immediately identifiable than the more prevalent Royal Navy models because they had even more alterations. The bezel was a completely new one, with minute markers all the way around its circumference, rather than just for the first fifteen minutes. These models were satin finished on the sides, to avoid the reflectivity produced by the usual mirror finish. The watches were delivered from Rolex Geneva to the Bexley Kent, headquarters of Rolex UK; they then went from Bexley to the Royal Greenwich Observatory, run by the Admiralty, where they were tested for both timekeeping and waterproofing. Only once they had passed these tests were Rolex actually paid for the watches, they then were returned to Bexley who were responsible for their shipment to the various naval store depots around the UK. Interestingly, the movement was also special, these watches were still non-chronometer, plastic glass ref. 5513, yet they had the hacking seconds feature, something that was only introduced on the chronometer models there years later.