This protection circuit for symmetrical 28 V power sources was found in a 1968 EEE documentation. The circuit can be adapted to use modern equivalent components.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This preamp with several inputs using germanium transistors from the time was found in Japanese...