This incredible First Day Cover of the 100th Anniversary of Baseball stamp was signed by the 1939 World Champion New York Yankees. The envelope has been printed with a portrait of Abner Doubleday and an action photo of a batter in a modern major league game. The First Day Cover was postmarked June 12, 1939, in Cooperstown, N.Y. Incredibly, almost the entire 1939 Yankees team has signed the piece, including captain Lou Gehrig, who had played his final game on April 30. The front of the envelope has been signed by Gehrig and manager Joe McCarthy (though McCarthy's signature is a clubhouse one).

The reverse has fourteen other members of the World Champions, including Hall of Famers Joe DiMaggio, Bill Dickey, and Red Ruffing, plus Tommy Heinrich, Charlie Keller, Frank Crosetti, Red Rolfe, Babe Dahlgren, Bill Knickerbocker, Bump Hadley, Johnny Murphy, Monte Pearson, Oral Hildebrand, and Lefty Gomez (deemed a clubhouse signature). This 1939 team is widely regarded by historians as the greatest Yankees team of all time. Winning 106 games, the Yanks would claim their fourth consecutive World Series with a sweep of the Cincinnati Reds that October. This First Day Cover envelope exhibits the expected wear from postal handling, but the signatures, all in bold black fountain pen, display beautifully. The envelope comes with a LOA from JSA.