They are generic game pieces. I'd expect that the rest of the over 60 bunch here, remember these from games, drawers, closets and junk boxes when they were kids.

I was thinking about them driving home from work today. Turned or pressed? I also remember red and natural (because white would be colored) probably dyed, like the black, which are now blue. Paint would be more expensive.

Something I never considered in the past, but if I see some, I'll break one and see if it's Pressed, Turned, or Molded.

Yes they have ridges and they stack. Which would mean, one side is a dimple and one side is a circle, in the center? Otherwise, they wouldn't stack? (guessing) Concentric rings must be different on the two sides. Or they won't interlock when they stack.

My suspicion is, they pre-date the molded plastic checkers which would be cheaper to manufacture.