batsbrew
actually,
there are many instances of grungy distortion that go all the way back to the mid 40's...
Yep, amp distortion goes right back to when the first blues and jazz electric guitarists cranked their small tweed Fender and Gibson amps in a desperate attempt to be loud enough and found the distortion musically useful.
What made the Maestro different was it had an on/off switch and put out a very raw and almost square wave form accessible at any amp volume. Which, I guess, is why Gibson's record compared it to brass and sax sounds.
I quite like the Maestro. It's mid focussed and unlike the Fuzz Face doesn't massively ramp up the bass frequencies as the guitar volume knob is turned up, while still retaining enough lows not to lose all the "body". Sonically it was an over the top early example of the concept that eventually led to the mid-humped Tube Screamer and SD-1 and the countless overdrives based on the TS/SD-1 circuit.