George: A F grade hammer gun is a fun shooter with no added value as a collectible, original or blued. It was almost surely case colored and then blued later, but the work was offered by Hunter Arms. It would be a concern if the barrels were also blued, and done with hot caustic salts. If so, the ribs are likely to separate from the barrels.
Also be sure the barrels are marked "Royal Steel" and are not blued Twist.