When making tool handles ,a piece of glass was used by some homesteaders to finish smooth.
Not sure if pictured pieces long sides would work as a sandpaper substitute/scraper but easy enough to try it out....
If you are angry ,just turn it off.....(Kidding).
As a youth when visiting the dump ,the guy in charge carried a pistol.
We would shoot rats with dads pistol ,but the dump guy shot every tv tube that came in. Didn't want them popping later I guess.
If you look close enough you can see the small dots in the glass. I am pretty sure it's TV glass. Some knap it, I wont as it has some pretty toxic things in the glass.