WW2 RAF, USAAF and Army whistle, Number 58. These were originally used in WWI & continued into WWII and is still made by the original wartime supplier. The whistle is larger than the Air Ministry 23/230 whistle - it measures approximately 50mm x 23mm x 30mm. It is marked 'J. HUDSON & Co BIRMINGHAM' and the year of manufacture (1939 to 1945). It has the British (Empire) 'W arrow D' (War 'Crows Foot' Department) Marking on one side.
WW2 ACME Military Army & Air Force No. 58 Nickel Whistle War Department