There is no difference in the baseballs used in either league of the MLB.
There is no difference between baseballs used in the National and American Leagues. They use the same baseballs made under the same guidelines listed in the Official MLB Rules.
1998 NL MVPThe 1998 National League MVP was Sammy Sosa
The baseball could have been signed for a fan that only had a National League baseball on hand. The baseball could have also been signed during a World Series at a National League park where National League baseballs are the only baseballs available.
1978 Rawlings All Star Game BaseballsRawlings started to make All-Star baseballs in 1979 that features The All-Star logo. Before 1979 Official Major League baseballs were used. National league baseballs were used when the game was played in a National League Park, and American League baseballs in American League parks. Rawlings first started to make World Series baseballs in 1978 that features The World Series logo.
There are many manufacturers, but Rawlings is the only company that currently makes the Official baseball for Major League Baseball.
The National League Spalding baseballs along with the American League Reach Baseballs (owned by Spalding) were used in Major league baseball for about 100 years until Rawlings took over in 1977, and Rawlings have been making major league baseballs ever since.
American League baseballs with the Reach Trademark had Red & Blue stitching, and the National LeagueSpalding Trademark baseballs had Black & Red stitching up until about 1934/35 when in both league started using only red stitching.For more information, and pictures of the different Official Major League baseballs that were used, visit the link I left below. -Steven KeyMan
Before 1978 official league baseballs were used in the world series. When the World Series was played in the American League ballpark, an official American League baseball was used, National League ballpark, National League baseball. The baseballs were not specially marked for the World Series. Rawlings started to make World Series baseballs in 1978 that features The World Series logo.
Sammy Sosa of the Chicago Cubs.