Appearing at the end of 1956, the 550A differed from its predecessor by use of a full tube spaceframe with several rear supportive cross-members, rather than the heavier welded-up sheet steel internal structure of the 550. Construction of the curvaceous and sleek hand-beaten aluminum alloy body shell was outsourced to Karosserie Wendler of Reutlingen. While visually similar to the 550, the 550A could be identified by new louvered access panels behind the doors. There were small air intake ducts in the nose. Most 550As offered a small molded windshield in front of the driver and a headrest fairing, and a metal tonneau cover closed off the passenger side of the spartan cockpit.