This hand made art glass aventurine / lutz, uranium / UV glass PEEWEE marble is 1/2" (12.65mm) , in new condition and signed "Wald 13". It's from the Waldglass art studio of Rolf and Genie Wald. There are aventurine ( lutz ) accents, and the design includes hidden (unless exposed to a UV light) glowing uranium glass (vaseline, canary, Annagrun). This auction is for one marble, there are several views of the same marble in different light. In the UV picture there is a pink reflection from the black light.