It is called Cerrokote it comes in different colors and similiar color to Stainless Steel, it was on my Ljutic GB..............................DLS
I just had an 1100 LW 20 ga. Completely redone. W/extra 21"bbl. Cost was as follows: gun with original 26 inch bbl was 175$ extra 21 in. Bbl 50$ 80$ gunsmith charge to break apart gun and reassemble gun. I will look further As I feel the gunsmith charge was overkill but not sure. Work done at West Michigan Cerakote, Grand rapids MI