A few months ago T206 resource had it as unconfirmed till it was found in an ebay search. I'm about to head back to work but I'll find the thread in main forum when I get there. It was the newly discovered backs thread. I thought they had the most up to date listing.
Edit
http://www.net54baseball.com/showthread.php?t=145814
That's when it was first seen but if the checklist was wrong so be it