I've made celluloid shavings by scraping it with a razor blade. It burns just like gunpowder. In fact, isn't "gun cotton" the same thing?

The older red transparent dice are made out of the same stuff. For some reason the white, ivory style material lasts much longer. Red dice of similar vintage to these (1939) would be starting to crytalize by now. Maybe the opaque white pigment protects them from light.