I know some people might shake their head at the idea, but did it come in a group with any similar looking examples? For instance: if it came in a group from UK and 95% of the marbles were Veliliglass, Yasuda, and German Handmades...
FWIW, it doesn't jump out as any particular manufacturer to me, and my opinion would be narrowed down by process of elimination instead of any particular tell-tale feature. That's what leans me towards a hand gathered CAC with a bunch of surface wear, but I can't say I've seen one quite like it