This formation was masterminded by Giants coach Steve Owen and relied heavily upon Hall of Fame center Mel Hein for its success.
It also placed the backfield opposite the "strong" side of the unbalanced line, providing more flexibility in the running game (though less power).
[1] One major advantage of the A is the center could snap the ball to any of three players; typically to the fullback or blocking back for runs and the quarterback for passes.
[2] A great center like Hein was a major asset, albeit not essential, in running the A formation — however only the Giants used this set-up with any frequency.
The 1938 win was the last time the A brought the Giants a title, however, as George Halas' modern T formation began to dominate professional football after 1940.