Lately I have found Several uppers which can be choose offs from rebuilt M16A1 rifles getting marketed as "new alternative uppers". The "C" over the barrel would indicate a chrome chamber only barrel. But AFAIK, Colt marked the "C" up close to the muzzle on their early barrels, not under https://greatbookmarking.com/story18541160/5-essential-elements-for-colt-python-6-for-sale