The Burden family made its original fortune in horseshoes, reportedly shoeing the entire Union Army during the Civil War. For obvious reasons, the bottom eventually fell out of the horseshoe business, but William A.M. Burden Sr. and his brother, James, both preserved the family’s good standing by marrying Vanderbilts. William’s nuptials were to Florence Adele Twombly, who had inherited not only Vanderbilt wealth from her mother but also a railroad fortune from her father and who was raised at the legendary Florham, a New Jersey estate so vast that it eventually became a college campus.

The funds that the Burdens curated would be preserved and maintained by their son, W.A.M. Jr., also known as “Bill,” who established one of the first “family offices” in Manhattan, to manage his family’s wealth through investments and careful accounting. When not overseeing the family finances, Bill Burden was active in Republican politics, serving as the United States Ambassador to Belgium from 1959 to 1961. He was a New York society stalwart who could count on a table at La Caravelle and whose well-honed taste was reflected both in his presidency of the Museum of Modern Art and in his personal automobiles.

Over the years, the Burden carriage house was home to an ever-changing range of the finest cars that money could buy. Bespoke commissions from all the great coachbuilders flowed through the family office for Bill Burden’s approval: pencil drawings of suggestions from Waterhouse, blueprints from Brewster for the latest Rolls-Royce, and original designs by Gordon Buehrig to tempt the prospective Duesenberg owner. Burden did, indeed, buy a Duesenberg, as well as a Hispano-Suiza J12 and a fully one-off, black-on-black Speedster that had been dreamed up with Harry Miller and combined front-wheel-drive and a Miller-built V-16.

In 1936, planning on travels in Europe, Burden went to Mercedes-Benz for a 540 K, and as with his other cars, standard bodywork for the car was simply out of the question. Reportedly, his request was for a design influenced by the factory’s great racing cars of the era. By the time it evolved into metal, Sindelfingen’s commission, number 219611, had become the Special Cabriolet shown here.

After being delivered to Paris in August 1936, the Burden 540 K in its final form bore little resemblance to the contemporary W125. Instead, the influence of the car’s owner and the Miller-Burden Speedster is apparent in the separate fenders, its lack of running boards, and the monochromatic black-on-black color scheme, as well as the blackwall tires and very little exposed bright metal trim. French design influences also crept in, with a wonderfully sloped and flared grille, which channels period Delahayes, and curvaceous fender lines drawn to a teardrop taper, which were nearly identical to those found on the famed Autobahnkurier Coupes. Even the usual 540 K hood louvers took on a gentle roundness.

The car borrowed the idea of a spare inset and flush with the rear deck from the 540 K Special Roadster, keeping the wheel out of sight except from a direct rear view. Yet, with plans for “grand touring” in Bill Burden’s mind, provisions were made to mount a second wheel on top of the first, as is shown in some period photographs of the car.

Burden’s European touring in the car was cut short by the advent of World War II, and when he returned to the United States, his 540 K came with him. Later in the 1940s, the car was sold to its second owner, of Queens, New York, in whose ownership it was a daily driver until his passing two decades later.

In 1963, a young stylist in General Motors’ Oldsmobile design studio, Herbert Roy Jaffe, was introduced to the second owner’s widow by his friend Herb Lozier, author of the Mercedes-Benz tome The Car of Kings. Soon after, Mr. Jaffe was able to acquire the supercharged Mercedes, much to his thrill. Years later, while being interviewed for Car Collector magazine, he recalled that the car as-purchased was complete, aside from a missing front spotlight and the two shock absorbers, one of which was gone and the other broken. He was able to authenticate its history with both Mr. Burden and Mercedes-Benz, and he spent some 20 years preparing for restoration, eventually finding a pair of the rare shock absorbers one day while browsing Hemmings Motor News.

After some three decades, Mr. Jaffe commissioned the unique 540 K’s return to original condition at the hands of LaVine Restorations, of Nappanee, Indiana. Using copies of original factory photographs, the car was returned to very much its original appearance and condition; only the colors of the interior upholstery and top fabric and the finish of the wheels were changed.

Work was completed in 1993, and the car went on to be shown at numerous events, with award-winning results, before Mr. Jaffe finally sold it in 2003, after 40 years of loving stewardship. After time spent in the care of respected collector John Groendyke and another enthusiast in the American West, it was acquired by its present owner, the sixth since new.

As one of the most well-known, unique 540 Ks, the Burden-Jaffe Special Cabriolet has been widely featured over the years in numerous publications, including in Michael Frostick’s The Mighty Mercedes and in both volumes of Jan Melin’s Supercharged Mercedes-Benz 8: The Supercharged 8-Cylinder Cars of the 1930s. It was the subject of a feature article in the December 1995 issue of Car Collector, which was written by Dennis Adler, who went on to picture the 540 K in his book, Speed & Luxury: The Great Cars.

This spectacular Mercedes-Benz, being offered today to its seventh caretaker, is one of few truly unique 540 Ks, as it was custom-tailored to the whims of an American aristocrat by the legendary craftsmen of the Werk Sindelfingen.