This is the game used grand slam baseball that Hank Greenberg hit for his 36th home run of the year on September 18, 1940.  Greenberg hit 2 home runs during this game.  This was game 1 of the double header that the Detroit Tigers won 14-0.  Written in pen on the ball is ""Hank" Greenburg "36" Home Run Bases Loaded, Sept. 19, 1940".  "Spt 19-40 DET 14 Phil 0".  I'm guessing the ball was written on a day later and that error date was written on the ball.  It appears the ball was shellacked.