Yes , that is basically what they do.
The first 3 are chassis and the next 3 are model...so, a a parts guy or tech can tell all about your car with the inclusion of the secound set of numbers
Just telling me you have a 126 chassis means nothing if I have to go to a schematic ,etc...
The remainder of the numbers tell us if the car is LHD/RHD and if it is auto-matic or stick.. ..and the final #s in the series are the serial #, which parts guys use b/c of part upgrades, changes within a series/vintage, etc..

Nice system...

http://catalog.eautopartscatalog.com/mercedesshop/sophio/model.jsp?header=header.jsp&footer=&partner=mercedesshop&baseurl=http://catalog.peachparts.com/&year=1985&make=MB&clientid=catalog.mercedesshop&cookieid=1M30LAGSC1U20P7NXX