These were steel access hatches (You can see the hinges). They were on top of the two raised coamings with the three forward facing portholes.
The hatches were situated directly above the port and starboard Steering Engines. The potholes afforded natural light in the steering flat. The hatches provided means for repair and replacement of the steering engines. only one was in service at any one time.
On D deck in the steering flat there are two capstans shown which were intended as emergency steering. These would work through tackles P&S which are also depicted running from the capstans to the steering quadrant. In theory, these tackles could also be man-hauled, but that would be a daunting process. Most steering engines had a "trick wheel" (origin unk.) that would allow using the regular steering system should there be a breakdown in the telemotor or its hydraulic pipes. Also, the wheel on the docking bridge would have had a means of connecting to the steering engine, possibly through a rod and crank arrangement. All very standard stuff in the early 20th century. There was some fear of telemotor, main steering engine, and/or quadrant gear failure.
-- David G. Brown
(PS to Mike Standart -- do you recall that odd tandem wheel setup on the ship in Toledo?)