Beautiful art glass ashtray

Hello. This is a lovely heavy ashtray, with lots of bubbles, in a very pale blue/green "ice" color. it has a ground pontil. The underside is unusual. It has stepped levels or layers, one a soft triangle and the others more flowing and bio-morphic. I bought it from a household that had some really good mid-century pieces and less expensive mid-century items as well. Any thoughts as to country of origin and maker? Photo of base to follow. I tinkered with the color a little on the first photo because it was washed out by the florescent light.