Originally Posted By: Argo44
WC commented above: "Nitro proof relative to BP proof."

Curious about "BP proof." You guys know this but might clarify what this is and when it started ended.

Here is a line about Zapatto Freres gun with a BP on the barrel we never identified; is this the BP referred to? http://www.doublegunshop.com/forums/ubbt...2760#Post442760



Argo, I can't find any French proofmark that used the letters BP. It'd also be very unusual to find a proofmark on the underside of the rib.