The LtGreen ground wire is soldered to both poles (center). The Pk wire is soldered to the 2nd & 4th throws; the DG to the 3rd & 4th. So throw 1 grounds nothing; 2 grounds Pk; 3 grounds DG; 4 grounds both.

It's POSSIBLE that this switch is equivalent, but I haven't confirmed that:
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Owner caption September 2011 · Photo 150 of 401