This circuit comes from a Gernsback Publications of the 90s. The circuit uses a general-purpose transistor as a sensor. The power supply must be symmetrical.
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...