Military Hamilton 3992B HS3 deck watch with Decimal dial c1940

This is a top grade Master Navigation pocket made by the Hamilton Watch Co, USA and used by the US government for military issue pocket watches during the Second World War. It was then sent to the UK where it was deployed by the Royal Navy and marked on the back with a broad military issue arrow and also HS3 markings.

After the war the HS3 deck watches went into storage at the Chronometer Section of the Hydrographic Department at Hertsmonceaux Castle; there during the 1950’s they had the enamel dials replaced with special decimal dials, using smaller hour and minute hands. This indicated that the watches “time-telling” ability is of only secondary importance to their main intended function. The dial layout gives emphasis to minutes, which are picked out in red on the intermediate chapter ring and an outer ring has been calibrated to indicate 100 unites per minute. These watches were particularly useful for the rapid mathematical calculations, where time equations could be more readily determined and expressed in terms of decimals. 

Source: A Concise Guide to Military Timepieces by Z. M. Wesolowski

This is a particular fine and rare example as it has the original American military markings AND the UK government issue arrow on the movement – the first time I have seen this variant. Plus it comes with its original box with labels

Movement – the high grade nickel ¾ plate movement has a lever escapement, a capped escape wheel and lever and a micrometer regulator. The movement has a wheel positioned on the top plates – this is for the centre seconds wheel on the dial. The movement is decorated with damascening and is signed “Hamilton Watch Co, USA, 3992B, 22 Jewels, U.8 Navy, BU Ships, Adj Temp & 6 pos, 3C421 and it is engraved with a government issue arrow also. The movement also features a hacking function – when you pull out the winder the sweep centre seconds stops – vital for synchronising watches

The movement is in 95% mint condition – light scratches

Case – the movement comes in a base metal open face case, which has a screw off back and bezel. The case has engraved contract details on the back “Navigation Master Watch, Mfrs part 3992B, Serial No.815- 1942 Hamilton Watch Co”. “HS3” has been crossed out and so has the original 815 serial number and the number 0552 / 520-8049 engraved on top along with a government issue arrow. The case has engine turned edges and is in 90% mint condition – light scratches on the back but overall a superb (and interesting) case.

Dial – the repainted dial has three chapter rings – see the opening paragraph for an explanation for the function. The dial is in 100% mint condition

The watch measures 51mm wide x 17mm deep

The watch has a synthetic glass

The watch is stem wound / stem set