Apparently they are glass. I couldn't tell if that knurling was on the inside or out... But yes it looks like it could be for a drive belt.
They are in individual flight cases and the police have lots of them.
Looks like something pinched from Area 51 to me. I hope they've checked them out with a giger counter... Wouldn't be the first time some fools pinched something with radioactive contamination. Hot in more ways than one... and not much fun for the poor souls who find it. I remember a story about radioactive iodine and some twit who took a fancy to the storage flasks.