Uncommon disc set, 1920s?

This one has me scratching my head a bit.  It was sold as a "Bakelite" set, though I find many people incorrectly ascribe sets to "Bakelite" when they are unsure of the material (or when they want to make their cheap plastic set sound more impressive).

This one is not, I think, Bakelite (I did the rub and smell test, as well as the "stick-it-into-hot-water" test and both were negative to my nose).  Some of the pieces bear small chips, revealing a slightly granualar/crystalline interior which sparkles.  Currently trying to research what it could be!