I don't know exactly what the switch does, but the mechanism looks similar to the one used in the Schaller Megaswitches sold byStewMac.
These are the new versions, the older versions looked just like the one that you posted.
I have several and like the mechanical feel and robustness.
If you list the pickup combinations, I could tell if this was one of these.
If you look at the instructions for the MegaSwitches, you'll see the different configurations that they can do, but you must list the combinations realized to be sure. I would suspect that you might have a MegaSwitch "E".