I agree, they look like imitations based on the drill hole, surface texture, and complete lack of any pearly orient, and the end caps next to the clasp. They are not very good imitations either.
P.S. I agree with Pattye that if they are sentimental, you may want to restring the better ones with other beads into another necklace. I have my grandmother's fake pearls that I wear occasionally and think of her when I wear them.