First day cover honoring the centennial of baseball, postmarked at Cooperstown on June 12, 1939, signed in fountain pen, "G. C. Alexander." In fine condition. This three-cent postage stamp honoring baseball's 100th anniversary was issued in conjunction with the dedication and opening of the National Baseball Hall of Fame in Cooperstown, New York, on June 12, 1939. One of the greatest right-handed pitchers of the teens, Alexander won three Pitching Triple Crowns during his storied career, and was elected as a Hall of Famer in 1938. Encapsulated in a PSA/DNA authentication holder.