I thought it looked home brewed....could be just about anything. What is behind the plywood panel that it is mounted to? There could be wires running through the base to whatever is there.
Pull the cover off!
The box is completely hidden unless you are on your knees in front of the head looking up. No wires come through the surface that it is mounted on. heading to the boat now, I'll photograph and update in a few hours...Stay tuned!