Original British WWII Wood Air Raid Gas Alarm Rattle

This is an Original British WWII Wood Air Raid Alarm/Gas Rattle in remarkably excellent condition. The upper wood surface is stamped with the suppliers ID of S21 in a triangle under a military Broad Arrow. Just above the crank it is marked D.S.W. and dated 1941. This example is very sturdily built, and even has a galvanized steel cover that produces the sound. There is a piece of wood attached to it that the clapper hits, making this extremely loud with metal resonator. The metal parts have a bit of oxidation but other than that it is fully functioning.