1972 911S Targa.. how to identify and value?
 

I have a lead on a 1972 911S Targa. I am trying to figure out how I can tell if it is a real "S" when looking at it. Please tell me what to look for.

Also what would you say a real '72 S with 150,000 miles, with a new transmission in overall 7 shape on a scale of 1-10 worth (estimate)?

Thank you!!