British Stamp Proof Mark Crown BNP

An English Probing Mark applied to a weapon, confirming the successful completion of Trials involving the firing of cartridges with a greater force than standard projectiles. It varies depending on the powder used in the test (black or smokeless, otherwise known as nitro) and the type of weapon on which it was applied.

Used in Birmingham from 1954.

Type of confirmation: Final Proof Mark confirming the completion of the test with nitro powder, usually applied to the breech and barrel