Landed this a few weeks ago from Bob. Looked to be an engineering unit; the part number of the motherboard is 610-0207, released motherboards are 611-0106.
Nice purchase, I saw this one on eBay and thought it looked interesting. I'd love to see some pics of the whole motherboard. I think it showed in the eBay pic that one of the logic roms was an eprom, so this lines up with it being an early engineering board.