Mine is 260K7XX I was just about to do a thread on this same revolver. I picked it up in a local Pawn Shop. It has the "F" stamp on the cylinder and a 2 1/2" barrel, round butt. It's about 90% to 95% condition wise. What's confusing me is on the cairn it has the MOD 66-2 stamp but no serial # as with most S&W's. No box or paper work. Also what would be the ball park value?