The area forward of the rudder post provided a mechanical assist during turning. 

As the rudder moved away for center line water hitting this forward area provided energy that helped turn the rudder.

The rudder could turn 35 degrees to port and 35 degrees to starboard.

Today, the rudder is 14 1/2 degrees to starboard according to the rudder angle indicator in the Steering Gear Room.  Photos in Todd's Shipyard shows the rudder turned to starboard.