Here's an e-mail I received from the seller regarding the "911SC" on the ID plate:
SC in the top left corner of the vin plate refers to Sport Carrera which is how the RS was referred from 1973 on for Euro models. That is sport Carrera the same denotation as on the RS, the name was later diluted in 1978 by the introduction of the SC as we know it today, check out the vin number on this site: http://www.adelgigs.com/911vin%20numbers.shtml