Description: introduced in 1913 for Naval service in the Webley & Scott SL Pistol Mark IN, which was not intended to replace the Webley revolver, but to go on issue alongside it. The cartridge's approval was later extended to Land service (mainly Royal Horse Artillery) and Air service. After the First World War, the cartridge's use was restricted to RAF and Naval service. During the First World War, supplies of Webley Self Loading pistols were supplemented by quantities of Colt Government Model pistols, which were readily adaptable to the .455 WSL cartridge. The RAF continued to buy such Colt pistols in 1919. While the cartridge was well designed, it offered no advantage over the .45 ACP, so never achieved any degree of popularity outside British military circles.This appears to be a commercial cartridge of late manufacture, probably shortly after the Second World War.