My blue Mercedes is a 1959 300d Adenauer, the little’d’ indicates a fourth series car, not to be confused with the big ‘D’ used for diesels.  The 300 Mercedes ran from 1951 to 1962 in four series, the last ‘d’ (like mine) were the first 4 door cars with standard fuel injection!  This system evolved from the system introduced on the 300SL Gullwing sports car in 1955. I bought mine in 2000 as a 30th birthday present for myself. It is one of 2 300ds this color and the only civilian car equipped with the parade horns mounted above the front bumper. Many 300ds were used by various governments and some of these feature them. My car is also one of the first Mercedes sold with Air Conditioning!  All 300s feature an overhead cam engine, 4 wheel independent suspension, and load leveling in the back. My car additionally features power steering, brakes and and automatic transmission. It was about $13,500 new. 

James