I have a Colt D.A. .41, serial # 136xxx, in very good condition, no rust, bluing with some very minor wear, bore clean and rust/pit-free, mechanically sound according to a local gunsmith. I was wondering where would be a good online source to find out the year it was manufactured (last pat. stamp is Jan. 19, 1875) and more general history about this Colt. What is this piece worth (ball park or approximate price range). Any info. would be helpful. Thanks.