This is only tangentially related to early high-quality materials, but since I'm already strolling down memory lane: My dad used to work as an after-hours maintenance tech at a graphic imaging company. For several years my mom worked days and my dad worked nights. Occasionally, my brother and I would get to go to work with either parent to give the other a break from watching us every day.
Going to work with dad was fun. Somehow he determined we wouldn't be able to do any harm, and let us sit at some of the editing stations (Macintosh Quadras of some type, iirc) and mess around in Photoshop (I think version 5.0 or 6.0?). Of course we got to digging through the files. One of them had a couple folders of some pin-up photoshoots. Incredibly high-resolution scans displayed proudly on a 20" Applevision CRT rivaling the size of our home television. Photos that would have taken an hour to download over the web if you could even find a place hosting them. We were too young to really appreciate it, but thinking back, that's an experience I'd be willing to bet none of my peers had.
There was also a folder of promotional monster truck material and some photoshoots from car shows. We were definitely more interested in those.
Sitting in that warm cramped room surrounded by 8 workstations with TENS of gigabytes of spinning rust will forever be a core memory. I miss the old HDD sound.