I think it is a condensed version of the larger foldout postcard...
http://sports.ha.com/c/item.zx?saleNo=716&lotNo=81071
At first glance, I thought maybe it was the same as the above postcard just with the other pieces missing (shown here intact)...
however yours actually looks like they used McGraw's photo as the outside cover (schedule found on back plus the brown color tone) instead of the Polo Grounds. That's why I think yours is actually a condensed variation. Nice pickup.