I inherited the Ruger from my brother. The 13.5" barrel has no markings. The front sight is ramped front sight with a white dot blade dovetailed in. Rear sight is an adjustable peep sight. I also have a 7.5" Ruger marked barrel that is in a plastic tube for the 7.5" length. Frame S/N is 70xx (1962?), 3 screw, non fluted cylinder. Can someone identify barrel origin for me? Ruger special order?? Thanks!!