S&W 58 with Adjustable sights

[Nightowl]

It sure looks like you have a Model 58, that someone turned into a Model 57. If it shoots, I wouldn't worry about it, if you got it at a good price. Perhaps back in its history, its owner couldn't find a a 57 so made the conversion. Who knows at this stage.

 

[steelslaver]

I doesn't take long to machine a frame for adjustable sight. Getting it dead level in my machine vice with brass inserts on each side is the hardest past. The sight tang is just a touch over 1/4" wide, so I make several passes with a 1/4 end mill to get that, usually deep enough the old groove is gone , but some times a little bit is left right in the center. Then cut the rear ledge using the same mill and an old sight body to get it just right. but, the depth is just a bit above the top of the hammer cut out. Then a short pass with a 3/32 end mill starting on the body ledge going forward for the center of the slot for the elevation stud, then another with small a modified key way cutter and your done. I still have a small 2 flute end mill I had modified to do the slot under cut before I found a key way cutter that would work.

When I drill and tap the screw hole. I uses a tiny set of vice grips with brass pads to hold the tang in place, drill the hole and then stick the tap in the chuck and turn it by hand.
Here are some shots from when I was making a J&G 10-7 into a adjustable sight 327 Federal

On K frames a long tang sight body will go all the way to the barrel and the very top will get flattened just right when you do the slot.

On N frames where body drops down with rounded top at barrel to fame junction. I simply machine a spot there and silver solder a piece of old tang in it like on this Brazilian.

 

[Pantherclass2004]

No matter what it is, its a nice gun