[Lynn Eades]

The balls are quite hard. The cups are like a brake lining - may even be ferodo.
Yes they are riveted in. I put mine in with Araldite - not yet proven
Alex if the balls are nbg, why dont you put the word out, and ask about the cups at the same time.
I think the cups would be hard to make, because of the shape, unless you found a modern material, in a sheet form, that could be pushed into shape. I think thats a big ask.