Along with a large amount of science and engineering equipment, we also have manuals that come from our Science & Engineering Equipment Technical Manuals collection. While it might seem that mid to late 20th century manuals would not be very exciting, I remember one patron who got quite excited about one of them.
Airborne Instruments Laboratory instruction manual for Type 125 Power Signal Source
Hewlett Packard X-Y Recorder 7035B
The Owen Laboratories Type 160 Time Calibrator