The number of bars left are on the dash display. No need for Leaf Spy. http://www.electricvehiclewiki.com/File:Scott_3_bars_s.jpg is a 3 bar loser.
The said, we normally pay attention to figures like Ahr, SOH and Hx. For me, there's no point in looking at SOC.
There is http://www.mynissanleaf.com/viewtopic.php?p=455984#p455984. There are numerous threads here where people have posted their stats w/some or all of those numbers and how many bars they have or what their stats were when they lost a bar.
Unfortunately, it seems like (can someone confirm this?) that if some unscrupulous person reset the BMS/LBC, all of those values will be inflated until the BMS/LBS is done relearning the battery which could take weeks or months of usage.
You should really find out where the car previously resided via Carfax and/or Autocheck. If buying a used '13, the build month is important.