If the quality is there I don't think it would matter if it was pattern welded tubes and black powder but I'd like to see a pic of the marks as post 1893 pretty much most of the examples were Nitro proofed due to the fact that they may have been imported into a country with proof laws. Also with Siemens-Martin steel tubes, right off I can't remember seeing a set with black powder proof only. If it is true, pressure is the key to use and Kent/Gamebore, Polwad and RST have cartridges as well as will oblige you with their data.
Kind Regards,
Raimey
rse
