I just went with your description but after looking again I think Larry is right. I believe the earlier ports had 4 pinsLarry N. said:Looks to me as if the lower (red) one is chassis. The gray thing above looks to be a place to plug something in, perhaps a diagnostic port? It certainly doesn't look to me like a switch.
JSplaine said:The grey thing I believe in not all there, seem to me there was something over those four pins.