Orry is right. It is almost impossible to date a 21 without a letter from the Cody Museum. And a lot of the paperwork is missing. But you might get lucky. #9411 was made in 1948 and #10407 was made in 1935. It may cost you to find out this info unless you are a member. But I would guess yours was made around 1935 or maybe before. Good luck......P.S. Do you own the gun?