Well I guess that's because I'm talking about the 20th century.
Any way why are you so bothered about it "Proof"? You dont have proof law and would not want it .
THe word choke was originally stamped on guns that were recess bored , choked guns were stamped "not for ball". After 1896 the word choke was stamped on barrels ,usually the left if it was choke bored.In those days people bought guns that were bored to what the gun maker decided was correct. Either a driven game gun ,a wildfowler or a general purpose gun ,one barrel for close one barrel for distance.
Later custom made guns were ordered to throw a set pattern at a set distance with a specific cartridge or load.
I dont know when the word choke stopped being stamped and I dont know what was common practice in other countries, but I do know what was going on in the UK particularly after 1950.
Boring chokes has never affected Proof status, I assume that marking guns in the past was to prevent people from blowing the end off their barrels by using ball or solid slug loads.
