Originally Posted by MTI
Perhaps you didn't notice the spelling of "Wagen" . . . which is the German designation for personal motor car, not "Wagon."
I agree of course. The question started from 190E though and I guess it would be good to emphasize that the current designation of letter for different car models, A, B, C, E, S, R, SL, SLK, CLS, CLK, SLR etc. etc. didn't exist at that time. Like the E at the 190E is different from E320, which was explained. Didn't this letter designation appear somewhere in the middle of the W140 production, only the latest ones were Sxwz like S500.
190 used to indicate the small body when it came after the current E-class predecessors. My understanding at least is that this is why it had different flavours of 190, the basic 190, 190E, 190D and then the 190E 2.3, 2.6 or so, at that time they had to use the 190 to indicate the body model and had to add the separate engine size indication.
The previous post already was quite complete but there are several earlier threads adding more details. The forums front page showing different body types and their respective sales designations as well as the forum model guide give further info.