I was looking at my Grandpa's old Marlin Model 81 .22 that he gave me about 15 years ago. I think I remember he and my dad telling a story about when they went to get it. It was used then and my dad was about 10, so that would make the year 1955. I can't find a serial number anywhere on it. How can I tell how old it is, and what it might be worth. I'll never sell it, but I am kinda curious. BTW, it is a squirrel killing machine!