From Mercedes-Benz's own description of their car:

The CLS-Class Coupe
Unrivalled and Outstanding
A completely unique vehicle concept generated by a powerful new vision. The CLS-Class – the first four-door coupé from Mercedes – combines the dynamism of a coupé with the luxury and practicality of a saloon. Now you can get your pulse racing, and still have space for four adults and their luggage.

Of course, the four-door coupe is not unique: think Rover P5B coupe. The term "coupe" is derived from the word "cut"; a coupe traditionally was a cut down carriage. I think it can be applied to any fixed head sporting car with a low roof line. As for "S", in "S-Klasse" it is indeed for Spitzen, but then in "SL-Klasse" it is now for Sports and once upon a time was for Super. It is unlikely to be for "Spitzen" in the CLS because that car sits beneath the CL which is, of course, the coupe S-Class.

Merecdes' nomenklature, like its build quality, has gone to pot!

This is all off-topic, though.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190