Hi Shem150, and welcome to Pearl-Guide.
Immediate first impression: they look like imitation pearls to me. They are very uniform.
But to be sure, do these tests:
1. Gently rub one pearl against another. Genuine nacre is a bit gritty/resistant to this motion, while imitation pearl-like coatings will be glide more smoothly. However, grime can make the pearls a bit gummy/resistant. If you feel resistance, try giving them a gentle bath in warm soapy water and test again after they are dry.
2. Examine near the drill holes. Often there is excess coating built up near the drill holes (although not always, not with better imitations.)
Also, if the coating has peeled off anywhere, you may be able to see the glass bead underneath.
3. If you have a loupe, look at the surface. Real nacre is very smooth at 10x magnification, while imitation pearl coating will look a bit coarser, a little like orange peel.