Found a voice encryption unit from a British military helicopter: the crypto hardware itself was removed (as expected), but there's a lot of interesting interface & digital encoding stuff built out of op-amps/comparators/4000-series logic, and a complex 3D construction scheme with lots of wiring harnesses.

https://www.eevblog.com/forum/projects/avionics-teardown-reverse-engineering-a-(de-mil)-voice-crypto-unit/