In my opinion, even asking about round count on a 40 year old gun kind of marks a person as a noob. No one's going to know, and it really doesn't matter. Unless the guy specifically said "I bought this brand new in 1978" or whatever. A gun with 10,000 rounds can be near mint, a gun with 100 rounds can be junk. Let the condition speak for itself. I've taken to logging all the rounds I shoot though a gun, but it's really just for my own benefit. Not really even benefit--more like entertainment.