It is too funny. You guys are just going to confuse him to no ends.
OK. R129 is the SL that we all refer in this particular section of the forum. R stands for roadster, and 129 is the chassis number (if you look at the Porsche, they call the 964, 930, 993 and 996 as 911. 993 and 996 is just the chassis designations of one of many 911 series cars).
W124 is the E class. W actually stands for Wagon. It is a 4-door sedan.
W163 is the M class, the SUV.
We like to use chassis numbers to throw people off
As I mentioned, I am not sure if the guage is at all accurate but there is no reason for me not believing it. My R129 is a 320 (6 cyclinders, if you must ask).