Not too long ago I've viewed Several uppers which are consider offs from rebuilt M16A1 rifles being bought as "new replacement uppers". The "C" to the barrel would suggest a chrome chamber only barrel. But AFAIK, Colt marked the "C" up near the muzzle on their own early barrels, not https://seek-directory.com/listings12965850/detailed-notes-on-colt-python-6-for-sale