Here are some links to repair tips and reference material.
460 Series / 475 Repair Tips (video)
The 4051 had three firmware releases during its production. This July 7, 1976 document details the corrections and the serial number breaks for the various releases.
4051 Firmware Releases
We don't know the source or reason for this document which describes the more popular transistors used at Tektronix.
Everything About Transistors
This undated document describes the phase-in of earthtone colors instead of the traditional Tek blue.
New Color Scheme
- 7L12 Spectrum Analyzer Plug-in
- Casting a Replacement Knob
- 468 +5V Storage Supply