IMGP5642
This is one side of the "Mechanical Signaling System" used to give information to the gunnery crews. The oval shape to the left is apparently a cast concrete megaphone. This is one leg of a "Y" shaped structure and there's a mirror image of this on the other side leg to signal the other gun pit. The numbers were changed by cranking a wheel inside the building at the base of the "Y". The numbers provided the Elevation and Azimuth for the gun crews. And the mechanical gears still work.