Prior to small arms entering service, they were inspected and then had an ordnance stamp applied to them. This was commonly the ‘broad arrow’ for British service. Examples of those on Vickers machine gun components are shown in the slideshow. They include stamped and etched examples. Those on the extractors are often very lightly etched freehand.
At the start of the Second World War, the British had to accept small arms that were non-service pattern. This included, for example, the Vickers M1915 through the lease-lend scheme from the United States of America and was used by the Home Guard. To identify these from service-pattern guns and ensure that the right ammunition was used they were distinctively marked according to Army Council Instruction 1571 of December 1940.