The classic car world would have been less interesting without that legendary New York importer of exotica, the late Max Hoffman. Were it not for his vision, Porsche might not have made the 356 Speedster, Dustin Hoffman's 'Graduate' would never have driven an Alfa Spider and the 252 examples of BMW's financially disastrous but desperately desirable 507 simply wouldn't exist.

But perhaps Hoffman's greatest gift of all was the 300SL, the futuristic road-going racer that he encouraged Mercedes-Benz to build when north America's wealthy sports car fans were living in a sci-fi age. And, with its scissor doors, 'egg crate' fender vents, fuel-injected engine and aircraft-like cockpit, the 'Gullwing' must have seemed other-worldly when it was first unveiled at the 1954 New York auto show.

The 'SL' in the name originally stood for 'Sport Leicht', a designation chosen on account of the car's lightweight, tubular chassis – but, even before a fraction of the 1,400 standard cars had been sold, Mercedes-Benz engineering boss Dr Fritz Nallinger had already hatched  a plan to make the Gullwing all the more more spectacular by  developing an even lighter version specifically for privateer racers. With only 29 built, the 'Leichtmetallausführung' or 'Light Metal' Gullwing is now among the most coveted of all post-war Mercedes-Benz models – and the example pictured here is possibly the most interesting and most desirable of all, hence the $7 - 9m auction estimate it will carry when it crosses the block at RM Sotheby's  in Arizona on January 27.

The Light Metal Gullwings were so called because of the paper-thin, aluminium bodywork and optional Plexiglass side and rear windows that helped to reduce the car's overall weight by a useful 209 pounds/ 95 kg. Add to that  stiffer suspension and a high-performance NSL engine with competition cam, high compression cylinder head, bespoke throttle valve and re-calibrated injection metering and the result was a potent and responsive, 215 horsepower racer that was more than a match for the quickest sports cars then  available from Aston Martin, Maserati or  Ferrari.

A mere handful of alloy Gullwings have appeared on the open market within the last 20 years, and few of those have been backed by such an interesting history as this one – a very rare and highly original survivor which is known as the 'African Alloy' on account of having originally been supplied to Moroccan Benz agent and enthusiastic racer Joseph F. Weckerle of Casablanca. Completed at the factory on May 27, 1955, it was delivered to Weckerle a fortnight later finished in Silver Grey metallic with a blue vinyl and gabardine interior. All of the Alloy features save for the Plexiglass windows were present, along with the addition of a 'high-speed' rear axle, suitably uprated 270 kph speedo and a Becker radio.

Perhaps unsurprisingly it was the only Alloy 300SL to have been delivered new to Africa - but its time on the continent was relatively short and, by 1962, it had found its way to an owner in Alabama who kept it for the following 13 years before selling it on to Dallas collector Jack F. Bryan. By then , the car had suffered a little as a result of nothing more than what would be considered normal use on a regular, steel-bodied example – because merely pushing too hard on the gossamer-thin alloy is sufficient to cause a dent, while the rough-and-tumble of racing can, inevitably, result in even greater damage.

To rectify any such problems, Bryan commissioned the world's leading 300SL specialist Paul Russell of Essex, Massachusetts to comprehensively restore the African Alloy, a job that took the best part of four years and cost the equivalent of more than $172,000 in today's money. What emerged from Russell's workshop was a car that looked every bit as good as it had done when it rolled off the Stuttgart production line in 1955 – helped, no doubt, by the fact that the original bodywork had suffered remarkably little, with any necessary 'stress' repairs having been confined to the engine bay.

With a fresh coat of factory-correct paint, a re-trim to original specification and the addition of a matching luggage set, the African Alloy was once again ready to roll – and proud owner Bryan's method of shaking it down was to drive it the 1,800 miles back to his Texas home. The quality of Russell's restoration was quickly demonstrated by the car's faultless performance throughout the trip, and it was soon picking up trophies at concours events – not least the 'Best Gullwing' award at the Gullwing Group's 1980 national meet  which, two years later, led to an offer to buy from none other than the group's president, Hyatt Cheek.

Cheek owned the African Alloy until 2014, completing numerous rallies in the car, attending Mercedes-Benz events far and wide and touring it extensively while maintaining a strict maintenance schedule. Now, however, the current owner of eight years has decided to offer this remarkable - and remarkably usable - rarity for sale to the highest bidder. It's undoubtedly a once-in-a-blue-moon opportunity. But as that $7m - 9m estimate suggests – lightweights need not apply…

Photos: Patrick Ernzen © 2021 Courtesy of RM Sotheby’s