I had a nitro converted revolver years ago when they first began to emerge. First point, as with your friend, I chrono’d mine and was also surprised at the very low velocity. It was a .36 cal and with ball gave an average of 565fps! That’s a ME of just over 50ft/lbs! But, I lived with it as the ES was very, very low and this consistency equates to very nice groups at 25yds!

Secondly, the proof marks were displayed on the barrel, frame and cylinder and on the barrel was etched something like; (3.0gns Herco. #209) with a proof mark after it. That was the load and primer it had been proofed for.