They are asking about the last 6 numbers of your vin #. This number is actually the production number. So your car was the 334292 W123 body to be built. To figure out Vin numbers, it gets a bit confusing. Prior to 1981 MB cars were numbered starting with the actual chassis number. In your case that would be 123. The next 3 numbers would be what version of the 123 chassis. For a wagon it would 193, a 300D sedan would be 133 (I think). For model year 1981 to present. the Vin numbers changed all together. They started with WDB which meant built in Germany by Daimler-Benz. Look at a new MB and it should say WDC (Daimler-Chrysler) The numbering also changed. The actual chassis number isn't listed by it's actual chassis number. My 2 TD's chassis numbers are W123.193 and W124.193, but this is not listed in the vin number since they were built after 1981. I hope this sheds some light on your question.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member