We know they're SPA, in Belgium... and though they are cut and shaped like Ivory...


...along withe the horizontal shave to receive the denomination...

...I do not see the first sign of Schrager (cross hatching) lines along without seeing any signs of them being Bone...

...or even early Celluloid-type plastic, I see posts (archived) suggesting they are Ivory.

Granted, we know some elephant tusk ivory can be a bit tricky but, after close study in bright, natural light, we finally find proof but, in this case I see no signs, whatsoever.