Richard-
I too am not an expert, but it also looks good to me (although it is impossible to tell without it in hand). One reason I think it looks good is that I have never seen another. Another reason is that I found a similar age baseball broadside (with a large blank area that was never filled in like yours) several years ago, and it was definitely period. It had similar aging spots as well. That is the best I can offer without holding the item and learning about its history of possession from the current owner (e.g. if this was an antique shop "find" I would be more suspicious than if it had been in the owner's family for 60 plus years). If it is real, I hope you can acquire it at a fair price. It looks really cool!
Alan Elefson
aelefson@hotmail.com