I totally agree with BP's comments regarding the two distinct finishes. Has the paint been burned off the hot silencer I'm bound to ask? They do get VERY hot! So far as the ground welds are concerned, I don't think that ground or un-ground welds on the mag housing are indicative of an S gun. More indicative of the manufacturer of the mag housing or at a particular time during the war. Ground welds were a spec. requirement later for the Mk5 guns