Glass or plastic?... your opinions please:

The bead(s) in question is on the far right of the closeup, the clear frosted ribbed melons.

The seller seems unsure, except she knows the large bead is bone. She calls the necklace 'substantial'.

Do you see any clues to convince you one way or the other? It would be far easier if I could see chips, but I see only bubbles.

I feel this might be the same mold used for my red bead. Did old glass molds get used in plastics factories after plastic beads began to be produced in Europe?

Or is this another case of a seller who can't identify materials?