Gents, IIRC that cap that fits over the gun muzzles was stamped out of stainless steel to eliminate the corrosion associated with the gun powder residue. I believe that it was held in place by countersunk philips head screws. It could certainly be primed and painted, but I suspect that is was simply brushed (mat finish), bare metal in this case.
Bodhi would likely know for sure.
My regards,
Widewing