Understanding MB Chassis nos.


I would like to understand the chassis nos. system for Mercedes Benz cars. I want to be able to identify various different models including S Class coupes from chassis no.s from an importers sheet. Is there a key to identifying the model type from the first part of the chassis no? e.g.. is S400HVEXC the S class coupe? or does that apply to any of the current model S Class. Thanks.