I'm am surprised by your confidence that what you say is accurate.

As near as I can tell, both old and recent palm-nut beads have been readily available since the '70s—though it's true I have not had the need to source any in recent years, because I have plenty.

Offhand, I don't recall ever seeing any African strands that combine palm-nut beads with "Celluloid" beads. In any event, I would not think of it as a common presentation. I wonder whether this is your perspective because you have only collected African beads for about ten years. Whereas my memories go back to the first wave of African collecting. That might account for different perspectives.

I'm not sure what to say about 'Celluloid being replaced by vinyl.' I am not confident the older disk beads (that are actually sequins) were made from Celluloid. I suppose cellulose-acetate might be a possibility. But, in fact, I'm uncertain how I or anyone would go about actually dating these different versions/editions of beads. JDA.