This is design by John Hollis. It’s a booster that uses an inductor to generate a massive boost. It also has a switchable octave up. The boost sound is very warm and clear. The octave has a nice tone also.
There is a drop in volume between the octave and the boost, since the octave has to push the signal through a diode ring. This made it impractical to make the octave switchable with a foot switch. Hence the toggle.
I got the 3DPT toggle switches from FutureLec for a very reasonable price. I had to wait weeks for them. FutureLec is slow as mollasses, I would not recommend them if you are in a hurry.