It is a very desirable Burke & Atwell Supplement issued by The Baseball Magazine in 1910. These are scarce and are quite coveted by collectors.
Below is a link from a Hunt Auction in 2005, which is the only time they've featured an original one of these (it has been reproduced, so be careful). Please note the price realized, and the fact that this one was in rough condition with a repaired tear. It is tough to find them any better (if at all) but like any other panoramas, the condition and price are closely linked.
http://www.huntauctions.com/LIVE/ima...=961&lot_qual=
You could consider re-framing yours, to conceal much of the water staining along the edges. Although many collectors prefer the original frame, no matter the condition.... simply a matter of preferance. Below is a shot of mine. It's one of my favorite panoramas of all-time, and really captures the essence of the fabulous dead-ball era...