Marbles from Africa? That's another good question. I can't remember if I've ever heard of them. My first thought would be marbles made for Codd bottles. For some reason that image pops to mind.
As to your first question, in my Scrabble group people were speaking of something negative associated with Nigeria, and the group administrators were concerned about Nigerian members feeling stigma from that.
That made me think of how in our marble groups, we speak of something negative associated with Bulgaria. And that got me to thinking about how Bulgarian collectors might feel after reading it. And that got me to wishing we had some Bulgarian collectors.
No real connection! Just my wandering thoughts.