The British Ministry of Defense (MOD) commissioned Rolex to create a military-issued dive watch tailored to their specific requirements, resulting in what is now famously known as the "MilSub." These specifications included fixed spring bars welded to the lugs to prevent the use of a reflective bracelet, a durable nylon strap (supplied by the Phoenix company), a 60-minute bezel insert, large sword-shaped hands, and a luminous dial. The MOD also mandated that the dials feature an encircled “T” to indicate the use of luminescent tritium. Casebacks of watches issued to the British Army were engraved with “W10” (the code for the British Royal Army), the NATO code “6645-99-9237697,” the issue number (in this case, “747”), and the year of issue, “77.”

After their decommissioning, many of these military watches were either destroyed by the MOD or sold to civilians and dealers, with most being modified to remove their military features, transforming them into more “civilian” timepieces. As a result, the present example is an extraordinary find. It remains in exceptional, unrestored, and fully original condition.

This particular watch is especially notable for its rare reference 5517, a model exclusively made for the MOD and widely regarded as the most coveted and sought-after of all Rolex MilSubs. Retaining crisp reference numbers between the lugs and on the caseback, along with its original military engravings, this reference 5517 is a truly exceptional timepiece. The original dial displays a beautiful rich patina on the luminous markers and sword hands, and it features the original “smudge-crown,” a term collectors use to describe the bolder Rolex crown.

Adding to its significance, this specific timepiece is illustrated in John Goldberger's renowned book "100 Superlative Rolex Watches", further cementing its place as a remarkable and historically important example of the Rolex MilSub.