It was the first coupe built by BMW after WWII and it was a disaster in financial terms.
It was built before the 507 roadster, which was another financial loss for the struggled German car-maker.

The war was over and the economy started to rise again. The American car-dealer Max Hoffman asked BMW to build a car to compete against the Mercedes-Benz 300 SL coupe and convertible. The 503 was introduced at the 1955 Geneva Motor Show and it was built as a left-hand-drive only.
With a design signed by Count Albrecht Goertz, the designer of the Datsun 240Z, the car was sold alongside the 501 and 502 sedan vehicles.

With the 503, the BMW said a firm goodbye to the pre-war forms, with tall and narrow engine compartments and curved, exposed fenders. The flush bodywork, with the doors and fenders aligned, was a modern styling. The long hood and short cabin featured four windows which could be lowered. It was more of a fake-cabriolet than just a regular coupe. The narrow and tall kidney grille was inspired by the last BMW coupe, built before WWII.

Inside, the 503 featured a luxurious interior for the era, with seating for four. It was offered with two different steering wheels, one with four spokes which looked like an X and another one with two spokes that evoked an airplane wing. The three dials on the dash were covered by a small lip on top. It was the beginning of the instrument cluster. A radio was mounted in the center.

The 3.2-liter V8 engine offered 140 hp. Unlike the 300 SL, which featured a direct injection fuel system, the BMW engineering team chose the classic carburetor system. The power went to the rear wheels via a 4-speed manual gearbox.