Going through the posts that Jamey links to, you can find a lot of information about the history and the misinformation that is around about these beads.

For a quick answer: these beads are wound beads, that were shaped while hot to create the five sides. Often, you can see that the middle of each side is slightly lower than the edges. This is a typical effect of working the bead while hot.
Together with Hans I have recreated some of these beads. They are pretty easy to make. Certainly easier to make while hot, than grinding each side down.

However, it does seem that most of your beads have been altered. They appear to have been cut into smaller pieces, like slices. The typical bead size is about 20mm, I think. You will probably find that they have one or two cut sides, and one (or no) more rounded side where you can see how the glass was wound.