I do not find the idea of an African origin very compelling for any plastic beads or artifacts in the early 20th C.

I assume a European origin is much more likely.

My assumption has been that a primary reason these small disks were made was originally for their use as sequins. They were made to be sewn-down, exposing their flat aspect. However, because they are perforated, it was also possible to string them as "beads"—and this happened to become a popular use for them in Africa.

Consider this. The flat surfaces are well-made. In contrast, the edges—which we see when a bead-use is pursued—tend to appear somewhat rough. The disks are mechanically stamped-out, and no work is expended to make the edges nice—as would usually happen in beadmaking. Conversely, why go to the trouble of making nice well-finished flat surfaces, for "beads" that, when strung, would never show this?

Granted, the beads/sequins are made from sheet material, and the formation of these sheets makes the flat surfaces smooth. But the formation of the disks (their stamping) does not suggest an intended bead use.

Just a few thoughts.

Jamey