Acoustat 2+2's help needed please

Hi,

I have 2+2's that haven't been hooked up for approx 20 years.  When last moved the housing was not secured and the wiring pulled away from the spade lugs.  There is also a pin that I can't for the life of me figure out where it goes.  

Would any of you guys be willing to help me figure out how these get reconnected?  I used/will use an Aragon 2002 amp for them fwiw.

Thanks!