Help Identify: Strange Sega CD / Genesis Adapter

Here’s a little mystery…

Recently, a guy named Henry sent me an e-mail asking for help identifying a strange Sega Genesis accessory.  I’ve come across one of these in the past and frankly have no idea what it is.  From these photos (which aren’t the clearest), you can see that it has a number of pins that connect to the Sega Genesis’ board where the Sega CD would normally attach.  When attached, it sticks out of the system slightly.  Thus, it seems like it must have a purpose.

Any idea what this is or what it does?