These E-Series Educational software hardly ever surface loose, let alone boxed. This is Pleasant Arithmetic (4th Grade) www.ebay.com
I have made an offer, but I doubt it will be accepted. I would really like to have it, but I'm not willing to fork out $200 for it.
Have you asked drx yet? Maybe he's willing to help to get this rare cartridge. Also this is for Mega Drive, right?