Margaret Thatcher

Exhibit features baseballs, bats signed by world leaders

Move over Mantle and Mays. Make room for Mandela and Gorbachev.

Randy Kaplan has spent the past two decades tracking down world leaders for their signatures on baseballs, a quirky melding of memorabilia and history that has resulted in an impressive collection of more than 200 autographs from presidents, prime ministers, two kings and the Dalai Lama.

"It's been a passion, a labor of love and an obsession," says the 50-year-old Kaplan, a lifelong collector whose day job is in government affairs for a real estate trade group.

It began almost as a fluke in 1996 when he positioned himself outside a speech and got then-President Bill Clinton to sign a ball. The...