Still curious as to what that Wily Wars cartridge was all about? Thanks to PRC reader Hypercoyote, we have our answer. Before the auction was taken down/ended, Hypercoyote contacted the seller, who had this to say:
"It's an eprom with custom packaging, everything looks like a real sega release, but it only came out in the europe and japan. I didn't do it (solder), I bought it off someone from the sega-16 forums. From what I can tell it uses an eprom with the euro wily wars on there with the game genie region patch applied, then soldered into a nba jam tournament edition game or similar since it uses a specific type of save feature. He made the art and manual himself."
Simply put, the cartridge was homebrewed--a fine homebrew at that.
Thanks for the info Hypercoyote and Jesse.