It looks a lot like mine that was stolen.
It was a gunsmith job with 2.5" barrel replaced with 4".
The frame topstrap does not match up with the barrel rib.
A 2.5" roundbutt has a thicker barrel rib and no step at the front of the topstrap.
If you put on a standard 4" barrel, you get that little jog there.
Maybe the Navy guns were the same, I have not seen one.