We found this bridge circuit in Electronics Now magazine from September 1995. The instrument can be from 50 uA to 1 mA. The trimpot value depends on this instrument.
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...