Serials of Nikon cameras & lenses:
http://www.photosynthesis.co.nz/nikon/index.html

Many Nikon manuals:
https://www.nikonians.org/reviews/nikon-manuals
http://ss-it.de/downloads.php

Many Nikon/Nikkor lenses repair tips:
https://diediemustdive.wordpress.com/2016/10/02/internet-nikon-repair-resources/