I believe they're called German circus marbles,they're very hard to find.
Here're some that were digged at Laucha,the colors are crisp and sharp.
Cees do you have pictures of yours?
Bob,I've got a German vibe from your marble,though,when I look at the first pic- in post #2,I hestitate a little,I have that kind of construction (pattern) not seen on my marbles,but maybe that says nothing,everything could happen.