Thanks for the shipment numbers, PC-Engine Duo was the PC-Engine with CD-Rom drive built in, do you know how much the original CD-ROM2 add-on sold?
Also, JVC made a Mega Drive with the Mega CD built in, called the Wondermega:
Any shipment numbers for this?
The chart I linked to above has SG-1000 shipments at 400,000, but Sega later released the Mark III, which was known as the Master System in the west, and later renamed as the Master System in Japan too. From the graph above I can see the Mark III/Master Sytem sold around 1m, but actual hard numbers would be nice.