Seeds Trust has this to say about it:
Seedsman Greg Schoen got the seed from Carl Barnes, a part-Cherokee man, now in his 80’s, in Oklahoma. He was Greg’s “corn-teacher”. Greg was in the process of moving last year and wanted someone else to store and protect some of his seeds. He left samples of several corn varieties, including glass gem. I grew out a small handful this past summer just to see. The rest, as they say is history. I got so excited, I posted a picture on Facebook. We have never seen anything like this. Unfortunately, we did not grow out enough to sell. Look for a small amount for sale starting in August 2011.
Seeds Trust was not, in fact, listing any Glass Gem corn seed for sale. They did have Golden Bantam, an old-time favorite variety which my father swore by. I grew some myself in our backyard one year as a kid. Golden Bantam takes forever to mature. Everybody else is eating fresh sweet corn and you have weeks and weeks and weeks yet to wait, but it really does taste better.
Geekologie has some more photos of Glass Gem.