I polished my first year model 12 and sent the gun to Glen Rock blue. My polish was not especially high (maybe to 320 grit) and there were pits left in the receiver instead of being worked out. They hot blued the gun, and it is very presentable. I was simply interested in my hands not getting rusty when I used it-it had been a barn gun since the late 1940s when I got it.
They did a great job, and the cost was reasonable.

Best,
Ted