At the first Frankfurt International Motor Show, which took place six years after the war in April 1951, many novelties were presented, including some cars of the top class. Apart from the 220 model, Daimler-Benz unveiled another new design, which was even more popular with the public: the 300 model, the biggest and fastest serial car of German production of its time. This soon became the favourite car for representative purposes in politics and in industry. We can justifiably desribe it as the true successor of the "Grand Mercedes" of the pre-war era, even though it was never officially given that name. Among the first important personages, who were chauffered in the 300 model were Chancellor Konrad Adenauer, President Theodor Heuss, Finance minister Ludwig Erhard and Social Democratic Party leader Kurt Schumacher, to name only a few.
The reason why the 300 model was first and formost linked with the name of the first chancellor of the Federal Republic of Germany and why the people and fans of vintage cars call it the "Adenauer Mercedes", is the fact that "der Alte" (the old chancellor) would never be chauffeur-driven in anything else but a 300 model, even when he was travelling abroad. During his term in office as Federal Chancellor until 1963 and then until his death in 1967, Adenauer had had six different 300 models. His first official car from 1951 is exhibited today in the "Haus der Geschichte" (house of history) museum in Bonn. The 300 d model of 1959, however, which Adenauer used after his retirement, moved into the ownership of Daimler-Benz and is on display in the Mercedes-Benz Museum.
Like the 170 S model, the 300, too, is not purely a post-war construction. Technically, as well as conceptually, its roots go back to the 260 model of 1940, which did not move into serial production, because the war interfered. Like the 220 model, the 300 was powered by a six-cylinder engine with overhead camshaft. In its first version it delevered 115 hp and reached a maximum speed of 160 kph. Framework and chassis basically followed the concept of the 170 S and 220 models, but were adjusted to the higher weight and remarkable driving performance of the 300. The most important novelty was an electrically activated torsion-bar suspension. Under extreme loads - the upper limit was 365 kg at first - this acted as a levelling device for the rear wheels. Apart from the saloon, which was available with optional sun-roof if desired, there also was a five- or six- seated Convertible D. Production of the main series was launched in November 1951, after the preserial cars had been extensively tested.
In May 1954, the first Model revision package was under way. The improved version, internally called 300 b, had a more powerful 125 hp engine with a higher compression and was fitted with broader brake shoes as well as a vacuum powerbrake. Externally, too, some details had changed: the 300 b had swivel windows at the front doors, chrome plated stoneguards at the rear fenders and bumper guards at the rear and front bumpers.
In September 1955, at the third IAA (International Motor Show) at Frankfurt, another modified 300 model was on display. The new model, internally called 300 c, could be recognised by its enlarged rear window and broader tires. The profound changes, which had been undertaken were not visible on its exterior: Together with the 180 and 180 D models, the 300 c had received a single-joint cross shaft axle, guaranteeing better ride quality. Moreover, it was now available with automatic transmission as special equipment, which had not been developed by Daimler Benz, however, but was supplied by Borg-Warner. This so-called "Detroit-Gear" automatic transmission was executed as a hydraulic torque converter with two secondary planet gears and an integrated single-disk clutch for the direct gear.
Like its predecessors 300 and 300 b, the 300 c model was available with a sliding sunroof and/or partition wall if desired and could moreover be supplied as a four-door Convertible D. In order to ensure a more unified production and because demand was low, the convertible was taken out of the sales programme in April 1956 and produced only until June 1956.
A special version of the 300 c, was produced and delivered to the federal Chancellor's office after the Chancellor had expressed such a wish. The new Adenauer-car was fitted with sliding sunroof and partition wall and it also had a longer wheelbase, which had been extended by 100 mm. The rear seats were pushed 40 mm towards the back so that leg room in the rear part of the cabin was increased by 140 mm. In June 1956, this special design became part of the regular sales programme and in August the first new models were delivered.
In August 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 denoted a new construction with its own series for the model 300 d. Yet the similarities to the 300 c are obvious. The drive train and chassis were taken over from the predecessor, but only the long version with a wheelbase of 3150 mm was used. The most important technical advance was that the fuel/air mixture was no longer supplied by a carburettor, but by intermittent inlet manifold injection. In combination with higher compression this resulted in an output of 160 hp. The 300 d was supplied with the "Detroit-Gear" automatic transmission as standard equipment but on request manual transmission was also available. From March 1958 ZF Saginaw power assisted steering could also be ordered (but not in combination with manual transmission). From December 1958 Behr air-conditioning was available, making the 300 d the first Mercedes-Benz car to have this option. But with a price of DM 3,500 this was not exactly a special offer.
The body of the 300 d was modernized, especially regarding the roof and rear; through a more filigree design of the C-pillars, the area of glass could be increased by 30 %. The 300 c now had a “pillar-less full-sight body”, which made it possible to completely open the lateral windows, and was therefore designated as a hard-top saloon. Luggage space in the boot was 15 % larger than with the 300 c.
As well as the limousine, which, like its predecessor, could be fitted with a sliding roof and/or an partition wall, a Convertible D was also available from December 1958. The substantial price difference of DM 8,500 ensured high exclusivity and a low number of units produced.
Even more exclusive were four individual cars, which were built in 1960 on the basis of the 300 d. Three of them, Pullman limousine and two Pullman landaulets were built on an elongated chassis with a wheelbase of 3600 mm and with a higher roof. One of the two landaulets were fitted with a single armchair in the rear as an extra feature for and delivered to Pope John XXIII in December 1960. The second landaulet and the Pullman limousine remained in the factory as representation cars to be rented out to the government or other wealthy parties for special events.
The fourth individual car, which was unfit for representation purposes, was not meant for the eye of the public. It was a completely new bodied two-door estate wagon, which was used as a powerful measuring car in the test department for many years.