At least for those war surplus BSRs converted in the USA, the work was probably done in many places, and surplus gun importers probably shopped around for machine job shops which would do it for the lowest price. Those done in England often had the converter's name engraved on the frame. As previously stated, as the converted BSRs are not in original condition, they are not collectible. I sometimes see them priced high at gun shows, but those dealers are simply trolling for suckers who don't know any better.