We call them base C6's. There are different option levels above the base C6. Some being "1LT", "2LT", "3LT", "Z51", and "Z06". The 1, 2, and 3 are trim level packages. The Z51 and Z06 are preformance packages. The Z51 and Z06 came from RPO codes or build codes.
I would imagine that it is C6...