 Although finally classified as a "12 cm" gun the bore was unchanged at 4.724 inches.During the First World War, the Japanese Navy transferred 24 original Elswick-built and 13 Mark IVJ to Britain as part of their military assistance to the Allies under the Anglo-Japanese Alliance.In 1940, some of these weapons were emplaced in British coastal defence batteries; for instance, at Mersea Island in Essex.