Here is what Mike says…
1941 Marconi Volt/Ohm Meter fitted with a single knob Fuzz circuit.
Single volume control and fitted with a true bypass switch and LED.
This is a really rich, meaty sounding fuzz that works well for both single coil and humbucker pickups.
The Fuzz circuit is based around a single MPSA13 transistor and BAT41 diode combination.
For those that may worry about me destroying a piece of early ’40s electrical testing equipment.. don't. No holes drilled in case, nothing that can't be removed and restored to original. So don't panic.’