So, the internal pictures pretty much debunk any connection to the HD20 with one exception; the drive mechanism, model number RO652, looks like it may well share the same motor/platter/case assembly as the RO552 the HD20 came with. The electronics, however, are completely different. (This drive is a native SCSI unit, and all the circuit board in the case does is adapt the card edge connector to Centronics and provide an extension for the drive select jumpers. The HD-20 of course has that weird proprietary connector with goes to a separate IWM controller board.) As for the rest of the unit, while it may indeed bear some superficial resemblance to the HD20 externally the Rodime unit actually isn't much like it in detail. The HD20 is all plastic with the case split about 1/3rd of the way up and the faceplate attached to the bottom of the case rather than the top, the position of the power supply and the drive are reversed, the Apple unit uses an enclosed Sony power supply module similar in appearance to an Apple II PS rather than a naked board, etc.

So basically it's a knockoff SC-20 that happens to share a weird bit of DNA with the HD20 in the form of that drive mechanism. It does make one wonder if you could swap controller boards from an RO552 that has a broken motor or damaged platter onto an RO652 and make a working Frankenstein drive... which of course will work another month or two before the 652 chassis dies.