I picture this stuff being made in sheets for some other purpose, and the discs with holes punched out in quantity, perhaps from offcuts.
I've only ever seen them in 2 sizes but never graduated heishi-style as the coconut shell or ostrich/snail/seashell discs are.
would it have been used to protect or insulate electric wiring?
Is/was this polymer stuff a by-product made in Africa from african raw materials?