Without the FTIR test, there's really no way to know the exact composition. Note that the alkyd resin mentioned above is a modified polyester.

If you perform the reamer test (or very hot water, or hot needle), you can probably rule out Bakelite (medicinal phenol odor) and Lucite (a faint fruity odor). If you get a strong smell of styrene, they are probably polystyrene. If you get a faint smell of styrene, probably polyester or a modified polyester.

If you want to send me one that I can experiment with, I can compare it to the beads I have with known lab test results.

If you beads look really new and are MEK resistant, then the likely candidate is one of the alkyd resins (aka modified polyester) from China.