Well, Bose may not be known for their receivers but this is one nice looking stereo! This is the Bose Spatial Control Receiver which doesn't seem to have a model number on it but I believe it is considered model 551. It puts out 100 watts per channel and has a built in EQ for the Bose 901 series IV speakers. Bose also made a model 550 that had a built in EQ as well but only sported 40 watts per channel and had no spatial control.
Here you can see the slider knobs used to control the EQ for the speakers. The front of the receiver has a flip down panel to access the controls. Also, the power switch is on the back of the unit and when it is on you can still turn the unit on and off by touching the Bose logo on the front of the unit.
These Bose receivers aren't that common and it's probably due to the fact that not that many were sold. The sales copy explanation behind how the "spatial" effect worked was somewhat complicated and, of course, they were really designed to work with the Bose 901 speakers (though they could work with any speakers). So, may customers probably opted for a more simple solution to their audio needs. Nonetheless, these receivers do sell for decent amounts of money. In fact, if you're a Bose fan then one of these units is probably a necessity. I've seen fairly average condition Bose 551's sell for over $300.00 and one in very good condition sold for around $500.00.