My two cents:

One of the better looking added ribs I've seen. It could have been milled from scratch or pre made and adapted to this application.

I believe the brass is from brazing the steel rib in place and at the same time the brazing filled in some voids like at the ends of the rib at the muzzle and at the frame.

Clearly a cut barrel and homemade front sight blade. Too long to be the remains of an original front blade with original base milled or filed away. Especially considering the amount of the blade at the rear filed flush to the top of the base.

If it were mine:

I'd turn the barrel in a lathe and turn back the front sight base/blade a proper distance, then cut a proper muzzle crown.

Or file/mill back the front sight blade/base and use a brownells crown cutter to properly crown the inside and outside of muzzle.

__________________
Jim
S&WCA #819