THE GREATEST GUIDE TO COLT M16A1 FOR SALE

The mag release button had a horizontal line sample on it, vs . the round line sample found on The existing ones, see the image beneath for an case in point:    The "C" about the barrel would indicate a chrome chamber only barrel. But AFAIK, Colt marked the "C" up near the muzzle on their own early barrels, not underneath the handguards. Pic of F