Mercedes-Benz uses internal code names in order to differentiate its models. W203 is one of those code names. It refers to the C-class vehicles, manufactured from 2000 until 2006. W203 was first introduced in 2000, with 2001 as a model year. It features 3 body styles - a 4-door sedan, a station wagon with 5 doors and 2-door coupe.
W204 is the platform on which Mercedes-Benz built the C-class. It was first introduced to the public back in 2007, during the Geneva Motor Show. The W204 C-Class featured design elements from two other Mercedes vehicles - W221 S-Class and C219 CLS-Class.