Adam,
To my knowledge, the gun you have there is a Beretta 686 Black Onyx (or White Onyx) that has been enhanced by Orvis' special upgrades.
Bottom line, when I had to restore one I had I needed to use HK tactical finish on the receiver (Duracote) because the metal could not be blued or color hardened. I believe the receiver is Aluminum or an alloy thereof. Incidentally, the black painted on matte finish looked excellent and the gun did sell after full restoration for $3000, so it certainly didn't turn out as cheezy as it sounds. (the entire value of these guns are the Orvis upgraded wood with the leather covered pads and the 28 LPI checkering)
