You are correct, they are Briley chokes. They were installed in 1992, I still have the receipt from when my grandfather got it done. A little back story, this was my great grandfathers. He passed away in 1989 and my grandfather got it. It was rarely shot as it is in fantastic shape. I shot it a few times just for the hell of it, but that is it. My guess is my great grandfather ordered it with the stepped rib from the factory. He was known to do that to get what he wanted. He ordered a 61 chevy impala from the factory, then barely drove it. Kept it in a garage. Unfortunately my aunt has that car now, not me. If it was done by a gunsmith, I have no idea who. My great grandfather lived near Warsaw, IN.