Can be used as a shield, this old American documentation circuit offers digitally selected attenuation values from 1 to 0.0001. The component used is uncommon today.
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...