Okie if you google it you are likely to get as many different answers as people you ask. I've read from 2 to 7 yrs with the last year being from 1985-1991. I have one, I ran across it by chance and picked it up as a conversion project but changed my mind when I saw how rare it is. (now i don't know what I'll do with it) I called Ruger with my serial number and they put a manufacture date of "late 1984" on it. I have witworth's book, I'll check it and see if there's info on it and reply.