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Aaron M.Marty Quinn, you dog! That is a friggen' awesome piece of sports memorabilia! And here I thought you were just the King of PSA Non-Sports Cards.
To the OP, Marty's ball with the original signature shoots the value through the roof, but your general rule of thumb is the ball (if in clean condition) is worth about $700 - $1,000. If you have the Babe Ruth portrait picture box along with it, then you can double the value (at least).