The proof marks shown below will assist in determining nationality of manufacturers when no other markings are evident. Since the U.S. has no proofing houses (as in England, France, Germany and other European countries), most U.S. manufacturers voluntarily proof their firearms with a specifed style of proofmark (i.e. the interlocked ©WPª synonymous with the Winchester trademark can be fired using modern smokeless powder) shells. Pre-1850 European firearms oftentimes do not exhibit any commercial proof marks and, with the exception of an occasional barrel address, they represent the single hardest category of firearms one can research properly. Captured weapons from major wars occasionally show two different nationalities of proof marks. This is acceptable since the gun was proofed in a national proof house after original manufacture and again when the gun was exported to a different country as a military acquisition. Please refer to the References section in this text for proof mark source information.
Download the reference guide here: Proof marks.
