We found this circuit in an Electronic Design. The main integrated circuit is the 4017. The frequencies are determined by the RC circuits as well as the duration of the generated pulse train.
This configuration of PWM control with the LM317 was found in a Popular Electronics from the 90s....
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in Signetics documentation from the 90's. The circuit performance curve is...