Prototype of Monster Races for Game Boy on ebay - unreleased?

I've just stumbled over this Game Boy prototype on ebay: http://www.ebay.de/itm/371231288664

Does anybody know if this really is unreleased? I double checked the net and could not find any information about this game.

PS: It also seems that the guy is selling a prototype of Super Skidmarks for the Sega Mega Drive but several types of this development cart/prototype seem to exist.

 

I was the highest bidder, but I didn't want to go that high, the wife would have killed me.

 

I was looking at the auction, thought it would end up with more bids, collectors probably didn't notice the auction or maybe no one had interest in this game although it's unreleased.

 

I'll let you guys know what's on it when it comes in. Surprised to have gotten it so cheap.