Okay, after thinking about this way more than I should be, I have come up with this possible scenario. Based on the fact that they are located next to the battery bank test switch, I believe they are an engine electronic isolation switch. I would be willing to bet that the alternators are wired to them. In the event of a failed alternator, you could isolate that alternator by depressing the switch and have your battery for that bank charged by not depressing the other switch. And vice verse on the other engine. Both switches in the open position allows both alternators to run to all three battery banks (or two if you only have two). Sort of like an electronic battery combiner. I would remove the panel inside the cupboard behind the switches, find the wires and note the colors. Start tracking them through to the engine room to see where they go. If they don't go to the engine room, at least then you will find out where they do go.