Because the parts I'm shopping for list certain engine and chassis serial numbers that don't look anything like the last 6 digits of a VIN. I'm looking for some control arm bushings and some of the kits have "For models with chassis serial number through B711095" noted in their listings. I'm also going to need a new water pump soon and the listings I'm looking at say "For models with engine serial number from 10-018294 (M/T) and 12-268716 (A/T)." Neither of those serial numbers are part of my VIN (or any Mercedes VIN, best I can tell).