kef series C 80 questions


I just bought these speakers for a second system and have some inquiries.
1.  There are 3 speaker posts on the back...1 is negative and 2 are positive
    How and which ones do I hook up ?
2.  These speakers Model # tags are missing. I would like to confirm that they are C 80.
      They are floor standers with tweeter/ mid range and oval woofer.
       I checked photos and they seem to be the C 80's
Opinions please.
Thank you
rocky1313