EDUCATE ME: Newbie. Pictures attached! I have just received an Ithaca frame & slide from CMP. Rack grade SN #1854247. It has a “COLT 45 AUTO” barrel with “F” stamp. Any way to know when barrel was made? Only stamps I see are: 1. I think it is a “M”on front left side of trigger guard 2. “FJA” ...