In 1951, at the first Frankfurt International Motor Show after the WWII, Mercedes-Benz unveiled among other new vehicles the top-of-the-line 300 series.
It was the biggest and fastest German car in production.

The 1951 model was the 300 it evolved in a series of models with several modifications. While the 1951 model was not named 300 a, the 1954 version received the 300 b name and the 1955 model was the 300 c. All of them had an open-top version named Cabriolet D. In 1957, a profoundly revised version of the 300 model was presented, which, technically as well as regarding its exterior, was clearly different from its predecessor. The design number W 189 confirmed a new construction with its own series for the model 300 d.

The body of the 300 d was updated, especially regarding the roof and the C-pillars. As well as the limousine, which, like its predecessor, could be fitted with a sliding roof or a partition wall, a Convertible D was also available from December 1958. It was much more expensive than the closed version, which led to a very limited number of units produced.

Despite being a convertible, the 300 d Cabriolet D featured an Artic-Kat air-conditioning unit on the options list. Inside, the car-maker installed new seats, with better support for the back of its occupants.

A big improvement was found under the hood, where an inline-six unit was fitted with a Bosch gasoline injection system in the manifold, instead of a classic system with a carburetor. It was fitted as standard with a 3-speed automatic transmission. A manual gearbox was on the options list. The four-door cabriolet version was produced in only 65 units.