Has the design of the M367 ever changed?
In 2002, the M367 design was improved:
1) With high quality potentiometers made by Noble.
2) The tone oscillator circuit was changed so that all inputs are muted when the oscillator is activated.
3) The level control for the tone oscillator was moved to the Master potentiometer.
M367 units with the serial number beginning with L (or after) have these new features.