The factory lists SCs at 1160 kg....or about 2550 lbs....but the way they were optioned for US, the weight difference is negligable against the official US weight of 3.2 Carreras of 2760 lbs. I would be surprised if an apples-to-apples comparison shows more than 50-100 lbs difference.
Look for rhe serial number on the vertical right side of the fan housing support...and look also for the engine "type" number ( like 930/21) faintly impressed on the engine topside in that same general area , a bit back and hidden.
Here's more--->
http://forums.pelicanparts.com/porsche-911-technical-forum/121529-911-engine-codes.html