Devices (other than a SegaCD) that attached to the Genny expansion port?

[Icarus Moonsight]

Recently ran across a model 2 Genesis at a thrift. Normally I would have passed it by without a pause, however something interesting caught my eye. At the expansion port, where a SegaCD would connect to the Genny, there was an odd protrusion that extended past the case a half inch or so. Investigating into the oddity I noticed inside was a connecter with a PCB?!? The first thing that came to me (and my admittedly over-hopeful mind) was a region lock bypass but, I'd like to know for sure what this thing is. Any ideas?

The "thrift" is asking $40 for the unit and that is why I didn't buy it. I'll go back and pick it up if this thing turns out to be more than a replacement cover or something equally worthless though.