A Lot of rifles were being rebuilt, Primarily Vietnam period rifles. Ordinarily the barrels were replaced. Some samples of markings observed on replacment barrels include things like: The "C" around the barrel would indicate a chrome chamber only barrel. But AFAIK, Colt marked the "C" up near the muzzle on https://gunnerwxxvs.bmswiki.com/4833128/colt_python_6_for_sale_for_dummies