I just picked up my dad's model 10-5 from relatives who had been keeping it for me since he passed away a few years ago. It's a special one to me as it was my dad's. I know he had it for as long as I could remember. The serial # is C742xxx, I'm guessing it's maybe 65'-66' manufacture from the other comments here? Can anyone give me a better idea? Thanks! I'm really glad I finally got the gun back, it's one of the few treasures I still have of his.