Scanning micro fiches
While repairing PDP-11's, I often suffered from missing documentation. Especially the program listings of the "XXDP" diagnostics were not found on the web.
On the other hand, some guys I know had boxes full of DEC micro fiches. It took a while before I realized that all documentation was already at my finger tips.
To read those fiches you need an old micro fiche reader (easy to get). Much better is access to a micro fiche scanner to make PDFs out of them, so you can share them with others. Getting access to a high-volume scanner proved to be almost impossible, so I decided to build my own.