So many unnecessary tangents.

Really, this is a discussion for a different dialogue. There's no point in hijaking this thread. But to respond to your points:

The "horn composition" buttons came from an informed button-collector. One of the people who is often touted as being among the "informed people" who are supposedly "way ahead of bead collectors." I took this at face value, and I did not test those buttons that I recall. They are stacked in a vial somewhere.

In any event, they are not remotely like the buttons you show. And, in fact, they do look like horn—being tannish-gray (though not all the same color as I recall)—and like something you'd see on a nice tailored formal coat (male or female).

I am (reasonably) 100% sure the person who had the "fish bone" beads did not smell them and make some comparison. This was just a made-up story to make the beads seem more interesting. So there is no point in devising a rationalization why someone would say that about "fishy plastic."

But whether there are plastic or synthetic materials that are being mistaken for "composition" is another topic entirely. That is certainly possible in some instances. I am talking about stuff I am familiar with, and expressing my opinions about it—or about the topic ("reconstructed Chinese materials").

100 years ago (+ or -) composition beads were manufactured to become cheap custume jewelry exports from China. That's all they are.