The letters e.g CLS is the model. The letters at the end usually mean the engines cubic capacity e.g the SLK 55 has a 5.5 litre engine. The cgi means that it is a diesel and if a d is on the end it...
I don't know what you're talking about, since there isn't a "W" on a Mercedes Benz as far as I know. I think you're talking about the wrong car. :P Many models incorporate the letter W. In 1934 there...