This is a thin steel locker that was obviously added on later. It is the Flag Bridge storage locker,and it has flat hinged doors on the rear face as depicted in Lars' picture.
The hatch to the left is exterior access to the Captain/Admiral's at-sea cabin (I can't remember which one.)
I think drawing a door opening on the flat rear side of the are would be detail enough to represent it in 1/350 scale!
Volunteer, USS Salem (CA 139)
United States Naval Shipbuilding Museum
Quincy, Massachusetts, USA