Photo #: NH 44548 USS O-10 (SS-71) and USS O-4 (SS-65) At the Boston Navy Yard, Massachusetts, 28 September 1922. Note that O-4's 3/23 gun is in the extended (operating) position, while that on O-10 is retracted. Four-funneled ship in the right distance is the former U.S. Army Transport Mount Vernon. U.S. Naval History and Heritage Command Photograph.