T206 Master List @T206Resource
 

First, forgive me if I'm beating a dead horse with this but I am curious how accurate the T206 Master Spreadsheet is. It was last updated Feb 2013. Is this pretty much a static list as there have been no other discoveries or does it need updated? And what is a verified or confirmed source, does an example have to be a graded card ?

I don't know if any new cards need to be added to the list.
No, they don't need to be graded.
You can contact Jim Rivers and Tim Cathey directly to inquire, or they might just respond in this thread.

Jim Rivera?

Yes, Jim Rivera. I really shoukd proofread stuff before I hit submit. ;)