I just won this in an eBay auction as part of a lot and while I anxiously await its arrival I am curious if anyone out there knows exactly what it is. I think it is from the 1910-1918 Base Ball Stars Notebook cover series but I cannot find any examples on line for Christy Mathewson. He does show up on this checklist:
http://www.teamsets4u.com/checklist/1910s/1910note.html
Thanks for the help...