Military proof
Military Webleys were not specifically nitro proofed but were proofed with issued proof ammo and received military proof marks. Cordite ammo was approved for use in all marks of service Webley revolver.
Commercial Proof
There were two proof houses in Britain, London and Birmingham which used different proof marks. The rules of proof were altered in 1896, 1904, 1916, 1925 and 1954 and the marks were changed with the new rules.
Commercial proof marks were applied when a commercial arm was made or in the case of a military arm when it was sold as surplus on the commercial market. Webleys could bear proof marks from the 1890s to the 1980s under several rules of proof and from two different proof houses. There is no single set of nitro proof marks.