Help solve the great baseball mystery

[cardsfan22]

I have a really interesting mystery and would be grateful to anyone that has any insight. I am a huge lifelong Cardinals fan and my childhood hero growing up was Jack Clark. A few years ago Jack sold some of his personal stuff from his career including his two Silver Slugger awards and some home run balls. Recently on an impulse (I usually dont buy a lot of sports memorabilia) I bought his 300th home run ball from the guy Jack sold it to back in 2007. I received the ball and a letter from Jack stating this was his 300th home run ball that he hit while on the Padres on July 30th, 1990 and he even signed the ball "My 300th". There was no doubt in my mind that the ball and the letter were indeed from Jack Clark as there are also pictures of him signing the ball.

Now here is where the mystery begins. As I was looking at the ball I noticed that it said "A. Bartlett Giamatti" as the National League President on the front. Out of curiosity I looked up online and discovered that Giamatti had served as National League President from 1986 until his sudden death in 1989. After his death William D. White became the president. So my obvious question was how could this ball be from a game in 1990 with Giamatti's name on it as president when he had been dead for a year? I have talked to a few people and done a bunch of research but so far no one can tell me 100% if it is possible for a ball used in 1990 to still have Giamatti as president on the ball. Do you think a team would use balls that still had Giamiatti as the president in a year when there was another president? There was also the fact that the lock-out occured at the beginning of 1990 so I wasnt sure if that would make a difference as well.

Any help solving this would be greatly appreciated!