About 30 years ago I saw a similar shotgun at London Guns in Santa Monica, CA. It was almost certainly a modern upgrade by someone such as Pachmayr. I was told that it was a "Remington Special" by the proprietor. There is a small possibility that it came out of the Remington Custom Shop using left over parts. At that time I had never seen a Remington Special but I have since handled two of them at the Butterfield Auction House in San Francisco.