This circuit was found in Radio Electronics from the 90s. The sensor is an oscillator whose frequency depends on humidity, an uncommon component nowadays.
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...