Actually, it is a little more complicated than that:

W stands for [I]wagen[I] or automobile.

All chassis numbers in M.B. cars up to recently started with teh prefix "WDB" = Wagen Daimler-Benz, for example:

WDB 140051 1A 350612

The first three digits are the model series (140)
The next three digits are the type (051 = S500)
The 1 stands for Right Hand Drive
The A for Automatic
And the last six digits are the vehicle I.D. production series number.

This is the standard German and Worlwide chassis identification. Only in the U.S. it varies with the VIN number.

In-factory, the W is usually attached to the standard sedan model (i.e. W124), then the following variations are known to the chassis I.D. numbers (not model designation plates):

A: cabriolet
C: coupe
R: Roadster
S: station wagon (yes S, not "T", hence S124 was inside used for a 124 wagon) A slight out of factory variation was W124T
V: longwheelbase (used ONLY in the U.S.), the rest of the world referred to these models as W140L.

__________________
A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]