The things in the boxes are microfiche, an archival solution used before scanners were common. The images on them are fingernail-sized and require a bulky device (also pictured) to read.
I work with these things. A fiche is the size of my hand and can hold about 10x23 A4 pages, maybe 10x24 if very dense. Or one ginormous dungeon map, if you really wanted.