The Black Prince.

The SSK was the sharpest edge of the supercharged six-cylinder line Ferdinand Porsche created at Daimler-Benz — the W 06 family that ran from the S of 1927 to the legendary SSKL. The K stood for kurz — short: the engineers cut 450 mm out of the SS wheelbase until the driver sat almost on the rear axle, and what remained was less a touring car than a Grand Prix machine with mudguards.

Ahead of the driver sat seven liters of straight-six. Left alone it was merely powerful; flatten the throttle and a Roots blower screamed into the intake, force-feeding the engine to around 300 PS and announcing itself for miles. Mercedes warned that the supercharger was for seconds at a time. Racing drivers treated that advice the way racing drivers do.

In Rudolf Caracciola's hands the SSK won on circuits and mountain passes across Europe, and its lightened sister, the SSKL, went on to win the 1931 Mille Miglia outright. For a few seasons the white cars from Stuttgart were simply the thing to beat.

It was also fabulously expensive, brutally demanding and built in tiny numbers — so tiny that the total has never been settled: thirty-some cars, perhaps forty-two, depending on who is doing the counting. Most were raced hard and used up. One chassis, though, would end up living an entirely different life.

What Trossi commissioned, and from whom, is the mystery at the heart of this car. Decades later, the restorers who reconstructed its history found exactly two drawings of the new body: one attributed to Willy White, an itinerant coachbuilder about whom sources cannot even agree on a nationality — American by some accounts, English by others — and one in the count's own hand. Who refined the design, whose workshop hammered the aluminum, in which country the work was done: none of it has ever been established.

What emerged in 1934 needed no signature. A black skiff of a body lies over the SSK frame: a bonnet that takes up almost half the car, three chrome exhaust pipes bursting from its flank, and one unbroken fender line that rises over the front wheel, sweeps along the flank and gathers into a teardrop over the rear wheel before the tail closes to a point.

There are no bumpers, no top, no luggage space — no concession to anything but line. Nineteen-thirties coachbuilding produced few shapes this radical, and none on a chassis this brutal. The car was at once completely of its moment and like nothing else made in it.

Ralph Lauren does not call himself a collector — he says he simply bought cars he wanted to drive and one day found he had a collection. Into it, in the late 1980s, came the Trossi SSK, and to Paul Russell of Essex, Massachusetts went the job of bringing it back. Russell's team worked like biographers: documents and photographs preserved by Trossi's heirs let them confirm the layout of the dashboard from a picture taken in front of the family home, and keep the hand-painted reference marks on the tachometer that had been there since before the 1950s.

The results speak in trophies: Best of Show at the 1993 Pebble Beach Concours d'Elegance, Best of Show at Meadow Brook Hall in 1995, and the top award at the Concorso d'Eleganza Villa d'Este in 2007 — seventy-three years after the body was completed.

And in 2011 the car stood in the Musée des Arts Décoratifs in Paris, in the west wing of the Louvre palace, as part of "L'Art de l'Automobile" — an unsold chassis from 1930, exhibited as a masterpiece of twentieth-century design.