Perfect condition, fully operational.
The M666 is a synthesizer voice with twin VCOs but it´s a very experimental brutal one. It makes a lots of noise and distortion. External audio signals can be fed thru and destroyed by the module as well.
Besides two VCOs there´s a dual high gain amplifier and some VCAs inside as well as a filter and a ring modulator.
Soundwise the M666 is somewhere in between a detuned radio, a fierce distortion and a noise generator.
125 mA +12V