The British and Americans copied the Maestro FZ-1A with mods, but the British used a modded version by Gary Hurst and possibly Roger Mayer in the Yardbirds, and The Spiders From Mars. Maybe early Zep too. So that interests me, I want one of those, please. But we can't be sure what Jeff, Mick and Jimmy had inside their fuzzbox enclosures. But we can guess, based on the needs of a '60s guitarist.

In the late '60s and early '70s British guitarists used germanium fuzzboxes of varying design. Some would have been hacks of other audio devices, some imported US pedals, some copies and variants of US pedals and some homegrown pedals. British guitarists often used fuzz boxes instead of overdriven tube sound before master volume controls came out.

There is very little info on the Tonebender MKI. Legend has it that Vic Flick (James Bond Theme) got Gary Hurst to redesign the 3-transistor Maestro Fuzz Tone FZ-1A into something with 20- second sustain. D*A*M This became the Tonebender MkI and the Zonk Machine. Roger Mayer's Page 1 fuzz is another 3-transistor Maestro Fuzz Tone relative with an improved bias control. I have an Amplifier Corp. of America Fuzz King which is yet another 3-transistor Maestro Fuzz Tone variant, this time with a gain control instead of a bias knob. The Mica Wailer/Fuzzder is similar.

So to FZ-1A (much the same as the FZ-1) was the daddy of quite a few fuzzes.

The schematics are screenshots from a circuit simulator, some may not be 100% like the original. The Fuzz King is 100% though.