The circuit shown was found in a 1967 RCA manual. Modern equivalent components can be used. The SCR must be according to the controlled load.
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...