Simon.
As shown on my recent photo I guess these recesses are openings for the T bars to various external valves under the casing deck, thus no spindlewheels on the valves.To tell which hole goes to which valve is probably very difficult. My guess is that it might be in connection with bunkering of fuel, luboil, freshwater and that sort of thing. The location of the valves around the galley hatch was convenient for communication with the people in the engineroom, remember these were the days before walky talkies.
Tore