Lightly soiled J.Cronin American League baseball which was belted for the 537th Home Run of Harmon Killebrew's Hall of Fame career. The home run was hit on 9/5/1972 during a game between the Minnesota Twins at the Chicago White Sox off of Eddie Fisher in the form of a two run home run in the top of the sixth inning propelling Killebrew past Mickey Mantle (536 HRs) on the All-Time home run list. The ball exhibits appropriate use including surface wear and several pronounced impact markings with "537" printed in period blue ink across the Reach manufacturer's insignia quite possibly in Killebrew's hand. Sweet spot displays a blue ink signature of Killebrew with adjacent side panel inscribed and signed, "I hit this ball for my 537th career H.R. to pass Mickey Mantle, Harmon Killebrew". Signatures and inscription rate 8 out of 10. With a humble yet methodical approach to the game "The Killer" enjoyed an outstanding career with the Washington Senators and Minnesota Twins. He finished his career with a staggering total of 573 home runs surprisingly ranking as the fifth most in MLB history at the time of his retirement. Uncommon rarity with seldom seen primary source written corroborative inscription on the baseball itself. Includes full LOA from PSA/DNA: Ball: EX, Signatures/inscription: NM-MT