Baseball Magazine itself started in 1908. But not sure when the Spalding Guide/Baseball Magazine stamp dates to. It is not cataloged in Yee, Fogel, et al. There have been fakes of that stamp. Though it looks different than the one here:
http://www.net54baseball.com/showthread.php?t=193601)
There was a Baseball Magazine Ty Cobb edition in 1912, I think.