6 pin 3 state slide switch
Typical configuration very close to Dave Tweed answer (DPDT) except that if I understand your question properly, then your switch handle has 3 positions and not 2 (DPDT)
My guess is that the two middle pins are the Common pins. Sliding the handle to the right for example, would connect each common pin to its respective end pin on the right.
If I am correct then your 3 position switch should show no connections between any of the 6 pins at all when the slide is in the middle. Easily checked with a ohmmeter 
BTW I never saw a switch behave as per your assumption