Question for Subal Owners

I just noticed, on the top of my fisheye dome port, in front of the Subal logo and just proximal to the port hood, a small screw hole without a screw. Does anyone know what (perhaps a screw) goes here? I am not anxious to find out the hard way that it is of any importance....

Thanks,

My 9" dome port (not the fisheye) dosen't have such a hole. Could it be for the sun shade (perhaps to rotate it 90 degrees?)