What we have here is an Amstrad 386 PC with a built in Megadrive, essentially the same idea as a Teradrive but a little more powerful. Pretty nice machine that could do more than a Teradrive, included 16 bit digital stereo sound, Intel 386 SX 25 Mhz processor, excellent screen and a Megadrive on an ISA expansion board, also docking bay for the Mega CD. Some nifty tech people were able to use this machine as a low cost development system for Megadrive games.
However at the time computer technology was advancing by leaps and bounds (as it is still today) and so within six months of it's release it was horribly outdated. Not as rare as the Teradrive but still costs about the same.