The first baseball whacked over the fence at Yankee Stadium by legendary home run king Babe Ruth goes on auction Saturday in his hometown of Baltimore, part of a celebration marking the 100th anniversary of his storied major-league career.

The unofficial home-run ball, which bears Ruth's autograph, was slugged during a batting practice session before empty bleachers and a snow-covered outfield two months before the stadium officially opened in the spring of 1923.

"I would expect it to approach or pass seven figures," said Ken Goldin, president of Goldin Auctions, which is selling 126 pieces tied to Ruth to celebrate the anniversary.

"Mark McGuire's 70th home run ball sold for $3 million ... and that's lost some of its luster," he said, referring to the performance-enhancing drug controversies surrounding modern day sluggers.

Ruth made his Major League debut on July 11, 1914, pitching for the Boston Red Sox at their home field, Fenway Park. He later joined the Yankees where he achieved his greatest fame as a hitter, including crushing Yankee stadium's first official home run when it opened in 1923.

The authenticity of the scarred, sepia-colored baseball was vetted by experts, said Goldin.

New York Daily News reporter Marshall Hunt allegedly coaxed Ruth out of his hotel and into the new stadium to hit a few practice balls as construction neared completion. One of them landed in the stands.

The ball's current owner, Joel Platt, owner of Sports Immortals Museum in Boca Raton, Fla., has had it for six decades. He first learned of its existence in the 1950s when it belonged to the family of the construction worker who collected it from the stands and brought it down to the field for Ruth to sign.

Platt, 75, would not say what he paid for the ball, only that "for a young kid back then it was like millions."

Platt's obsession with sports memorabilia began when he was four years old in 1943, when he was injured and bed-ridden after a gasoline explosion. His parents entertained him with baseball cards, and that passion stuck.

He traveled the world, building a collection that includes a Brazilian soccer team uniform once worn by the great Pelé and a jacket worn during the 1960 Olympics by Muhammad Ali when the boxing legend still went by his original name, Cassius Clay.

Platt said parting with the ball will be difficult, but that it will help fund a larger space for his collection where he can show off hundreds more of Ruth's items.

Babe Ruth retired from Major League Baseball in 1935 as the all-time home run king with 714 career home runs. That record stood until Hank Aaron of the Atlanta Braves broke it in 1974.