Technics SA-C06
The SA-C06 was sold by Technics in 1982. It does not have a battery compartment, so it is more like a portable component system rather than a true boombox. It is often mistaken to be an SA-C07, but the control layout is totally different, and it has a manual tuner instead of a digital one. It provides a minimum of 20 watts per channel into 8 ohms between 20 and 20,000 Hz, and that's with only 0.8% total harmonic distortion.
The service manual can be purchased HERE.