This transistor curve tracer was described in a December 1969 Radio Electronics article. It consists of a ladder-type signal generator that applies stepped voltages to the transistor under test.
We found this circuit, which appears with variations on this site, in a European documentation from the...
This circuit that drives an electromechanical counter of the time was found in Radio Electronics magazine...
Found in a Hands On Electronics of the 80s, this circuit makes use of a gas sensor of the time....