Kennet specifically notes PSI. I don't know if that is incorrect, or not. I have a photo copy of the whole, rather lengthy article, and I will see about getting the charts in it scanned. Hope I'm not violating any copyrights.
After reading the Ideal info Wild Cattle graciously posted from Geoffroy's site, and seeing the timeline for production of lunette Ideals, including the years that R proofed lunette guns were available, the little old gun dealer in Lyon may not have had an actual fact, BUT, it seems like it's usually a pretty darn good rule of thumb. Proof with powder other than PT can't really be considered smokeless proof by today's, or even, post 1900 standards. Lunette guns were in production until 1909. Powder T became the only proof powder in 1914. A lunette Ideal proofed with powder T is likely a rare bird, not impossibly rare, but, rare enough not to matter today. Hence, a lunette proofed with powder J, M, S, or anything other than powder T, was smokeless proofed FOR THAT POWDER, IN THAT ERA. It really can't be considered to be smokeless proof by today's standards.
Best,
Ted
