Can't really tell without seeing the schematic (which I can't find). Maestro has a history of innovating rather than cloning, so I'd be more inclined to assume it's not based on anything. That being said, I doubt Maestro is the same company it was 50 years ago. And you really can't do anything completely original with analog audio circuitry anymore, so even if it was "original", I'm sure you could spot "inspiration" from other circuits.
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