Below are some approximate production dates that will help you date your Webley Air Pistol. Guns with BIRMINGHAM 4 on the side of the cylinder were made up to 1958 after which the 4 was Removed. This was to identify parts that were fitted to specific guns has they were processed round the factory.
Later Pistols were the marked with usually a threedigit batch number. Webley Mk3 Air Rifle Serial Numbers - truexup This rifle was manufactured for Webley in Germany by Mayer & Grammelspacher (Diana/Original) from 1985 -1989 and was based on M&G’s Diana/Original 124 Air Rifle.
Webley started producing Air Pistols in 1924 and today still produce Air Pistols to the same design principle (see below the Tempest) The early Air Pistols were marked with serial numbers up to the beginning of World War 2.