Herewith photos of my Hamilton 3992B, serial nr. 3C1772. I am interested in learning how these watches were used by the Royal Navy. First, some recent history: in a post January 13, 2013, DaveyG wrote: "On withdrawal from Naval service, the UK based [3992B] watches were returned to storage at Herstmonceux Castle . Some were subsequently issued to the Royal Air Force for use on the nuclear bomber (V) force.." Documentation which came with the watch indicates it left Herstmonceaux Castle on March 24, 1967. The case back is etched with the Air Ministry section and reference number "6B/60." So it's easy to imagine this was a navigational watch used aboard the V bomber of 1967, the Avro Vulcan. Back to the Royal Navy: another post in this forum (HUDD, March 12, 2016) notes a 3992B used by the father of its previous owner who served in HMS Quorn. The post indicates that Quorn was sunk after the previous owner's father was transferred. So, at least in this case, the watch may have been issued to an individual, not a vessel. The back is etched "NAVIGATION MASTER WATCH" and Whitney calls it a "Master Navigation Center Seconds Watch." Test tolerances were average daily rates not to exceed five seconds, and variation from the average daily rates not to exceed two seconds over five days. That rate variation translates to significant navigational error over time, so it's hard to believe the 3992B was issued as a master timepiece for extended periods. The 3992B is also described as a "deck watch." This most likely means it was a source of time throughout the ship after hacking to the chronometer, thus not disturbing the latter. In this role, it's similar to the U.S. Navy's comparing watch, the 2974B.