Mercedes diesel vans always have a three digit number plus 'd'. However, the number is not the displacement in litres. ie 207d. First number is the ton rating of the chassis--2 tons. The last two digits are the tens and ones place of the horsepower rating of the engine. 207=70 horsepower (European) or 216=160 horsepower. (with a few exceptions--for instance their passenger bus (309d) is not on a 3 ton chassis to my knowledge)
When imported officially to the US as Sprinter's the vans lose these European #'s.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13