500 K

The Type 380 of 1933 was judged underpowered almost on arrival — Sindelfingen's coachwork had grown heavier than its blown eight could carry with dignity. Development of a five-litre successor began in January 1933, before the 380 had even reached the Berlin show. A year later the 500 K appeared at the 1934 Berlin exhibition as a single streamlined Autobahn-Kurier, and the sales force called it the highlight of the show. Hans Nibel, whose all-independent chassis underpinned it, died of a heart attack that November; Max Sailer took over the design office on the first day of 1935.

The formula was aristocratic: a pressed-steel frame with coil-sprung independent suspension at both ends, hydraulic servo brakes, 12-volt electrics — and the M 24 straight-eight whose Roots compressor engaged only at kickdown, lifting 100 PS to 160. Untertürkheim built 342 chassis in three years; nearly all crossed to Sindelfingen, where Hermann Ahrens's Sonderwagenbau bodied them to order in eight catalogued styles. The bare chassis cost RM 15'500, most bodies RM 22'000, and Friedrich Geiger's Spezial-Roadster rose from RM 26'000 to 28'000 — house money, spent on a car.

In autumn 1936 the 5.4-litre 540 K took over, and the compact '500 K' label only became common once a sibling needed distinguishing. The market has since sorted the family with brutal clarity: original Sindelfingen cars trade from under a million dollars for closed coupés to $5.3 million and beyond for the seven surviving short-tail Spezial-Roadsters, while postwar rebodies and replicas — a cottage industry since the 1950s — trade at a permanent discount that only factory authentication resolves.