@Mr_NutterButter
The glass disc is not surprising. Magnetic hard drives themselves are made of a glass platter that is metal plated. They weren't always made of glass, but this is the modern way of doing it.

The interesting thing about traditional hard drives, and even SSDs, is that you'd think you could write something on them, then disconnect the drive and save it somewhere forever. But you can't. Even if you perfectly isolate them from stray cosmic rays that could cause a bit flip, hard drives will slowly lose magnetism over time, and SSDs will slowly lose those stored electrons. You can't use them for "forever" storage, and you're forced to constantly rewrite the data for long term storage, to completely be safe against data corruption.

The metal and glass discs work because you're not using magnetism to store the bits. You're etching into the materials with lasers. The technology is essentially similar to CD/DVD, except the medium itself is far more sturdy. And they're easy enough to read if you have lasers and know how to decode them.
But you could also create analog phonograph discs out of these materials, and use them for some more basic info on how to make a laser reader for the other discs. Getting sound from a phonograph disc is basically foolproof by comparison.