A WW11 c1943 RN issue Admiralty Pattern NO.6 crown-wind anti submarine 6 second stopwatch. The dial with arabic and baton numerals, stamped WALTHAM USA. 5cm diameter. Nickel plated nine-jewel stopwatch movement, caliber 16-43TA, signed and with an engraved broad arrow, serial number and PATT 6 to the reverse and attached to base metal watch chain. Used on board RN warships in connection with Asidc anti-submarine sonar device in order to plot the course, speed and range of the U boats. This information was then used to set up and launch depth charges.