Cees can you post the 2 pictures of the marbles,you've got from that man?
About the sparkler types,I really don't know where they have been made,I can found them in so many European country's and there are so many different type's at this moment I'm a bit lost.
I've a sparkler type with Bonux printed on it,i've also one with Bonux engraved,think the engraved one is older.
About the German striped transparants,they are different from the 2 seam German slags,the slags have a colored or clear transp- base with white stripes in and on them.
The striped transp- have a second or more colored stripes.They can be beautiful,Galen has a beautiful German striped transp-,I must have that picture somewhere in my photo files.
As for the clay's yes I know there was a factory in Amsterdam who made them.
Because i'm not so interested in clay marbles I have not done research,Read the article in the newspaper,if I remember well there was a picture of the inside of the factury.
Here's a bonux sparkler type.
winnie