The mess table photographed from aft looking forward and to port. Mystery solved! The device that looks like a large valve handle is actually the top of a C-Tube hydrophone. Under the handle is a graduated dial used to indicate the bearing of the tee (which is under the boat). The head set plugs in on the top of the hand wheel. Presumably this is a shot of the tubes in the "up" position. So the mess room doubled as the listening room. Thanks to Todd Woofenden for solving this.
