[drc]

A Jackie Robinson single signed baseball has value and an Ozzie Smith single signed baseball has value, but if you have Ozzie Smith sign a Jackie Robinson single signed baseball the value will go down. This is in part because single signed baseballs are a staple of the baseball autograph hobby, and a Jackie Robinson single signed ball is considered a prize. Adding a second signature, even if it is Ozzie Smith, George Brett or Brett Favre, isn't making it better in the eyes of many collectors. These collectors would say if you want George Brett's autograph, that's great, but have him sign a different baseball.