[Ron Smith]

It appears that someone may have tried to build a carbine, gave up and cut the barrel back to pistol length.

I think the slot and insert in the front of the frame has been milled to attach a stock / forend tenon. Is the metal insert removable, or held in with a cross pin? It's unfortunate that they used a Navy for the conversion.

If and when you post additional photos. Try to get some nice clear ones of the rear sight. If it's an original Navy sight in good condition. It would be somewhat valuable on it's own.