Interestingly it has a gold-plated 68008 processor onboard. It also uses the exact same square-shaped & coloured connector as the original Mac mouse and appears to have a serial pass-through port, along with a couple of internal dip-switches. The most amazing thing is it has NO power switch. It is designed to come on automatically when the Mac turns on. And it does all of this perfectly well.

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A serial pass-through port was common on serial port drives. Typical buyers were already using the two ports on the Mac for an ImageWriter and for a modem, so the pass-through port was a big selling point. Some drives also functioned as print spoolers for an ImageWriter.

The drive powers up by detecting the +5V line. Thus the drive will not work with a Plus onwards unless you provide an alternative +5V source.

See:

http://docs.info.apple.com/article.html?artnum=3202&coll=ap

The 68008 is unsurprising and would have been used as a general purpose controller. It appeared on a few third party NuBus serial boards.