This circuit is from a factory manual from the 80s. The circuit can be implemented with more modern operationals. Capacitor C1 is a low leakage type. 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...