I have been searching the net for awhile to get info on these proofs but to no avail. A couple look similar to Birmingham proofs but not quite the same. Specifically, I am interested in the proof house, war of manufacture and most importantly, if it is nitro proofed. The guy I bought it from said it was reproofed for nitro relatively recently (like the last 50 years) but the only thing I can see that MIGHT represent a "nitro" proof is the "NP" but that stamp looks to be as old as the others AND I am not going to "assume" that it means nitro proofed especially when most (all?) others I have seen actually SAY "Nitro proofed". Anybody know what I have here?. For the record, it is a J.W. Rosier, .410 SXS.