Proofing was one of the first things done, before ANY finishing operations. Note that the last "proofmark" (actually more of an inspection for functioning, since the barrel was deemed good at that time) was the (P) which was struck in the wood - no worries about buffing over. Yes, the receiver and barrel had different finishes - were they disassembled after once being joined? I was not there, but I'd have to say "NO". You can get a fairly decent picture of Krag fabrication from reading OM22. VERY little changed between 1878 and 1892.