Couple points: First, I see a 2 3/4, which tells me the gun's chambers have likely been lengthened, probably in the States. French chamber length often isn't marked, but if it is--other than on guns specifically made for export--the mark would be 70MM for a 2 3/4" gun. Also, the proof was with smokeless powder M (the PM mark), which means the gun could be no more recent than 1914. Since that date, only smokeless powder T (PT) has been used for proof.