Onkyo ZAC-55
This Onkyo is very rare. It was introduced in 1984 and had a recommended sales price of 209.800 Yen, which was about 945 USD! Very expensive for that time, but very solid in terms of built quality. It uses lots of aluminum and weights more than 10 kg!
There was an optional carry handle, enabling you to join the MR-55 tuner/cassette, MA-55 amplifier, and M-01 speakers into one set to carry. There was also an optional leather carry case with a shoulder strap and integrated battery. There's no battery compartment in the main unit itself.
There is also an optional stereo booster component, which was not provided in basic trim. This booster works like a power amplifier and boosts the bass.