The work is ok because the sight fits it. It looks to me like bare metal with milling marks. The machining done at the factory is much smoother than what I see in your photos. (At least on the dozen or so I've had the sight off of ) Regardless, it's a cool gun and I would letter. Also get S&WHF search of records. Never know what might turn up. Now we need Range Report!!
Below is pic of factory 3rd model target rear sight. It is a 1932 W&K gun. Note extremely tight lines. It is blued underneath, with matching # sight and barely visible machining marks. It is also a "Chopped" 3rd, lol.
1926 Chopped Target .44spl