This circuit was found in documentation from the 1970s. However, it can be implemented with modern transistors such as 2N2222 for Q1 and BF494 for Q2. The crystal depends on the desired frequency.
This circuit, with printed circuit board, is from an article in Radio Electronics magazine from...
This simple transistor radio with only two germanium transistors was found in a Japanese magazine from...
Found in Radio Electronics from the 90s, this circuit generates signals in the 60 Hz to 1.4 Hz...