Until 1994, Mercedes-Benz used an alphanumeric system for categorising their vehicles, consisting of a number sequence approximately equal to the engine's displacement in liters multiplied by 100, followed by an arrangement of alphabetical suffixes indicating body style and engine type.
"C" indicates a coupe or cabriolet body style (for example, the CL and CLK models, although the C-Class is an exception, as it is also offered as a sedan).
"D" indicates the vehicle is equipped with a diesel engine.