[Jim K]

The actual proof/acceptance marks on guns will often not conform exactly to those shown in the drawings (as opposed to photos) in books. The most obvious reason is that the books often show a "generic" or idealized mark that was not duplicated when the actual stamps were made. Then in older times there were many stamps, even in the same proofhouse at the same time, that were supposed to be identical, but were hand made and not exactly alike. Stamps also broke and would be replaced, often with one far from identical to the broken one.

Nor can we rule out counterfeits. While not common in Europe, fake proof marks and manufacturer's marks are normal in guns produced in the Middle East.

In modern times, stamps are made from a master die, so there is more uniformity.

Jim