Found in an American documentation from the 90s, this circuit makes use of an output transformer for transistors, working with a 6 V power supply.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
This source was obtained from a book on transistors from the 60's. The circuit uses germanium...
This powerful inverter provides a high-quality sine wave signal. I found it in a Radio Electronics issue...