The "Williamson, Brooklyn" studio stamping at the right edge of the mount was a key clue in the ultimate identification of the subject as the Atlantic Base Ball Club of Brooklyn, considered the first Champion of our national pastime, as well as the sport's first dynasty. The Atlantics served as a founding member of the sport's first organized league, the National Association of Base Ball Players, and held the Championship from 1859 through the war-shortened season of 1861 before finally surrendering supremacy to archrival Eckford of Brooklyn in 1862.