I think what you have there is a very nice hand polished reblue. The grit marks should be vertical but very parallel because they were factory polished on a large wheel. That rifles grit marks show signs of a hand polish because it's very difficult to keep them parallel. Also, if you look closely at the barrel stampings, you don't see any slightly raised edges that usually occur from the roll stamp. One more clue is the barrel turning a plum color as a hot blue will do after some years because of the high nickle content in the steel. From the color of the blue, I would say it was dipped in Dulite salts as they give a more blue look than some of the other salts used. Just my nickles worth.
