These seem like old-timers, but I don't really know.

8 sides seems fairly uncommon.

The layers seem to vary from 3 to 5, instead of the more common light blue opal or cornflower blue core with a dark sapphire overlay.

Also, the layers are wobbly, thick/thin in some places.

The white layer seems to be deteriorated glass, not white glass.

The concave sides are distinctive.

I don't know what caused the matte finish - wear and ground burial? Grinding? Cat litter? Acid cleaning?

Thoughts?