I think my sources are a little better....
This link is Nissan's microfiche stating that all S13's built between 7/90 (first month for dohc) until the end of production had the same piston (part code 12010).
http://carfiche.com/fiche009/s13/2/f03.gif

Then you take one look at Nissan's factory service manual for a 1993 240sx, page EM-43 and it tells you plain as day that the compression ratio is 9.5:1.