Just snoflecks, with a white glaze inside. The glaze totally covered the letters stamped into the leather hard clay, but make really cool textures in the 🚫 symbol!

Clay is actually reclaim which contained some speckled clay of the same type.

Kiln was programmed for cone 6, this shelf likely didn't get that far. Cone 5 witness cone was bent but Cone 6 did not bend.