Here is what Mike says…

Superstar Fuzz-OD.

One knob fuzz with gain switch. 

Built by MR-FX. 

Single transistor (MPSA13) based circuit hand wired on vintage style tagboard.

Volume control and gain toggle switch. Select higher gain for more sustain.

Note: an audible click can be heard when using the gain toggle switch at volume, this is perfectly normal for this circuit.

Requires external 9v tip negative, sleeve positive, standard pedal power supply.