Try the bead reamer test - run a diamond grit reamer in the hole and immediately sniff the sawdust - this may give you a clue if they are phenolic resin - you will get a strong "medicinal" odor.

Another idea - if you have household 10% ammonia - put a tiny amount on a q-tip and rub gently - if you get a mustard yellow color you probably have phenolic resin. I normally wash the bead in warm mild soapy water first, to remove grime, and you may not want to do that. You may still get the yellow color but it may be mixed with dirt if you don't wash the bead.

I have gotten the color change with dyed horn though. But these beads look like the type of round phenolic beads made for the African trade. Made somewhere in Europe, timeframe unknown - I am actively looking for more info about phenolic resin beads.

I also have beads that look a lot like these and they are polystyrene. I thought they were phenolic resin and I handled them in person before buying. Could they also be wood with a nice varnish?

In other words, a number of materials used for imitation amber look like your beads. If you want to send me one I can tell for sure.