Alvin Davidson used to make a lot of scope bases for Kelbly rings and maybe even manufactured rings. I do not believe he does this type work anymore. If I am incorrect I am sure someone will jump in and say so.
They probably are as Alvin quit doing them himself many years ago. Seems like his son made them. Might do a search on Davidson Tool in New Mexico. They had a pretty good size business and the shooting stuff was a hobby.
Butch