Used Univox Super Fuzz from the 70s. It sounds insane, the volume, expander pots are super clean. The footswitch has been replaced by a newer one (same brand and part number). We still have the original one, for all of you collectors out there. This pedal is sold AS IS.
This fuzz is an octave fuzz using two germanium diodes to produce the square wave clipping.
The controls are 'Balance' (volume), 'Expander' (fuzz amount), a two position 'tone' switch, and an on/off footswitch on top.
There are two unique features of this device that set it apart from other distortion and fuzz pedals. The first is that the full-wave rectification of the circuit produces an upper octave as well as a slight lower octave. This also gives the sound a lot of compression and gives a mild ring modulator effect. The second unique feature is a tone switch that engages a 1kHz filter that "scoops" the mids, giving a very fat, almost bassy tone, unique to this circuit.
Hughes, Tom (2004). Analog Man's Guide to Vintage Effects (FIRST ed.). USA: For Musicians Only Publishing. p. 25. ISBN 0-9759209-0-1