The Mercedes Benz S-Class W188 Series.

Is a luxury car coupe, cabriolet and roadster body that was manufactured between 1951 and 1958. Presented at the Paris Salon in 1951 it is mechanically similar to its predecessor. Mostly built by hand it was marketed as one of the most important luxury cars in the world. It has three Solex carburetors and an engine power of 150 HP at 5000 rpm. Subsequently replaces the independent low-pivot rear suspension and incorporates a fuel injection engine. Visually, it was distinguished by a chrome bezel on both sides of the hood.

Different versions were equipped with gasoline engines:

Mercedes Benz 300 S | engine M188 | l6 cylinder | 3.0 liters 
Mercedes Benz 300 Sc | engine M199 | l6 cylinder | 3.0 liters 
Source: Wikipedia

Actually, we have these manuals for the Mercedes Benz S-Class, W188 Series: