This 1937 Mercedes-Benz 540 K coupe was hidden in a Nebraska garage for 40 years

When Mercedes-Benz wants to swing its weight around as a longtime titan of the auto industry, it trots out the old slogan Das Beste oder Nichts—“the best or nothing.” That phrase may never have been more true than in the second half of the 1930s, when the Mercedes 540 K was the pinnacle of engineering, style, and luxury. It was the ultimate super grand tourer of its era, with stunning looks, a rockstar 180-horsepower supercharged straight-eight engine, an advanced independent front suspension, and plenty of room for two passengers and their luggage. Masterfully built in Mercedes-Benz’s Sindelfingen plant, the 540 K was nonetheless popular among coachbuilders, who could provide already exclusive clients with custom touches.

As Jake O’Gorman headed out to Nebraska to follow a lead about an old pre-war Benz, he never thought he’d uncover just this sort of coachbuilt 540 K—a one-off coupe conversion that was last seen in 1980. O’Gorman is a car specialist at RM Sotheby’s auction house, so he’s familiar with all sorts of rare and high-dollar vehicles, but his first barn-find-esque discovery made him feel like a little kid again. “It’s just such an incredible car, and I can’t believe how well it’s held up after being in storage for 40 years,” he says.

The car started life as a silver metallic 1937 Mercedes-Benz 540 K Cabriolet A (chassis #154143), one of four factory bodies available. The Cab A was perhaps the most beautifully designed, with its more expressive front fenders, rounded rear, and “set-back radiator,” which positioned the whole engine and transmission assembly 185mm farther toward the car’s rear. Mercedes produced 419 examples of the 540 K chassis, including 32 of the second-gen Cab A.

Originally delivered to Brabender GmbH (a still-extant laboratory instrument company), the 540 K’s next owner was the Henkel family, which owned a chemical works business. In 1951, the Henkels commissioned coachbuilder Hebmüller take off the cloth top and transform #154143 with a unique hardtop that would make it resemble a factory-built Mercedes 540 K Spezialcoupe. (Ironically, Hebmüller’s primary business at the time was to convert Beetle sedans to cabriolet form.) This work was exceptionally good; the adjusted roofline blends seamlessly into the car’s silhouette, and the new hardtop itself was properly integrated into the car’s structure. The project also included a new two-piece windshield with crank-operated windows, slight modifications to the body, freshened taillights, and a new metal cover for the dual spares mounted at the rear. By 1954 it had made the jump to the U.S., where it got a new two-tone, cream and grey paint job and a Golde canvas sunroof, and was sold for $3250 in upstate New York by Henry A. Rudkin Jr., son of the woman who founded the Pepperidge Farm bakery.

When the current owner’s parents bought this unique 540 K at auction in 1968, it had already been in Nebraska for several years. Once they bought it, they regularly drove and showed it at local events. Until 1980, that is, when the 540 K suffered an ignominious defeat at a county parade and car show—to an antique John Deere tractor. That was too much for the current owner’s father to stomach, so he indefinitely stored the Benz in a garage of his own construction. And there it sat for 40 years.

When O’Gorman saw the car for the first time in that two-car Nebraska garage, he knew it was a special moment. It wore the dust and dirt you’d expect, but the 540 K coupe appeared amazingly intact. There was a bent rear bumper, the result of the family often stepping up onto it in order to reach the garage’s breaker when the power went out.

RM Sotheby’s and the current owner agreed to sell the gorgeous pre-war machine at RM’s 2020 Arizona auction, which kicks off next week. It’s estimated to sell for between $1M–$1.5M, which is a reasonable range given its condition and recent 540 K sales. At Gooding & Company’s Pebble Beach auction last August, a barn-find 1941 540 K Cabriolet A sold for just under $1.3M, and Bonhams sold a 1938 model in February 2019 for nearly $1.8M. The most paid for a factory coupe at public auction was $3.08M in 2011, following the car’s concours-quality restoration. RM also handled that sale.

In preparation for the Arizona auction, RM Auto Restoration has been busy tidying up the Hebmüller 540 K to cross the block. Workers at the RM’s Blenheim, Ontario, facility aimed simply to make the old Benz look its best, rather than execute any sort of comprehensive overhaul. They fixed the bent bumper, buffed the two-tone paint, cleaned the all-original red leather interior, and brought the engine and brakes to working order.

“We didn’t have to mess with anything major in the engine bay,” says Don McLellan, president of RM Auto Restoration and an expert in pre-war mechanicals. “It’s a really complete car, and the chassis is so good it still has some of its original paint.”

The 5.4-liter overhead-valve straight-eight is a powerhouse, resembling an aircraft motor lurking inside the 540 K’s elongated hood. It makes about 100–115 hp when running with natural aspiration and its dual-updraft carburetor, but once the Roots-type supercharger engages (the K is for Kompressor) output climbs to 180 hp. The blower’s interaction with the rest of the drivetrain is what McLellan finds particularly impressive about the 540 K’s brilliant engineering. Additional forced-induction grunt arrives when the driver reaches a certain point in the throttle pedal’s travel, which has a spring that engages a set of clutches responsible for spinning the supercharger. On top of that, and to manage the difficulty of supercharging a carbureted engine, the 540 K has pipes designed to bring the fuel bowl to the same pressure as the jets. There’s also a pressure regulator for the triple-piston-driven fuel pump. Oh, and as all this is going on, the engine also adjusts its timing to account for the supercharger.

“There was really nothing like the 540 K on the road in its heyday,” O’Gorman says. “It’s a massive car with a massive engine, meant for just two people.”

On a cloudy afternoon on the grounds outside of RM Sotheby’s headquarters in Blenheim, those two people are O’Gorman and myself. We pile into the bench seat, awash in the scent of aged leather. We stare out of the split-vee windshield and over the mile-long hood. He twists the key, and the straight-eight starts right up. A shrill whine fills our ears as the supercharger whirrs—its usual wake-up stretch to help warm and thin out the engine oil. Once the blower shuts off, the engine settles into a nice, even rhythm. “The more we run it, the better it sounds,” he explains with a shrug.

Just for fun, O’Gorman flips on the dual front lights and big center-mounted bulb. He reaches down to a set of non-original aviation-inspired gauges, installed at some point to monitor the performance of the supercharger. Next to the cluster’s black dials sit a number of bone-colored switches, and he tugs at one of them to flip on the spotlight mounted at the Benz’s A-pillar. With an incandescent yellow glow leading the charge, we set off for a low-speed ride around the grounds, feeling like villains in an Indiana Jones movie. The car bounces along somewhat uncomfortably, which O’Gorman says is a symptom of its old, somewhat-square tires, which probably hail from the 1970s. (A new owner would immediately invest in fresh rubber as a first order of business.) Still, even with the bumps, the ride is an immensely satisfying sampling of automotive high life in the 1930s.

Fans and collectors with their spotlights trained on the Arizona auctions next week will have a chance to check out this 540 K up close. And if you’ve got a million-plus clams burning a whole in your old-timey trousers, why leave the tent with nothing when you can take home the best?