The price was right $3, for both. They were in a box of picked over loose rifle barrels and some airgun parts. They are steel, but are just castings, not drilled or milled.

Any clues as to origin?

United Sporting Arms or one of its later iterations. Can't remember which model these go to (Abilene, Seville, El Dorado), but they pop up more often than one would think. Neat find!

I saw they were set up for a coil spring, but I knew they weren't Ruger.