Together with its predecessor the 500K, the magnificent Mercedes-Benz 540K was arguably the most noteworthy production model offered by the Stuttgart firm during the 1930s, representing the pinnacle of its pre-war achievements. A development of the 500K, whose independently suspended chassis it shared, the 540K was powered by a 5.4-litre supercharged straight-eight engine. The 540K was one of the first models developed under Mercedes' new chief engineer, ex-racing driver Max Sailer, successor to Hans Nibel, who had died in November 1934 aged only 54. It featured the company's famous Roots-type supercharger system in which pressing the accelerator pedal to the end of its travel would simultaneously engage the compressor and close off the alternative atmospheric intake to the carburettor. This system had been thoroughly proven on the preceding series of Dr Ferdinand Porsche-conceived S-Type cars, and in effect the 540K was the last supercharged production Mercedes until relatively recent times.
Launched at the Paris Salon in October 1936, the 540K had an engine that developed 115PS un-supercharged or 180PS (178bhp) with the compressor engaged. The gearbox was a four-speeder, but with a direct top gear rather than the overdrive ratio used on the earlier 500K. With the supercharger engaged, the 540K's blown straight-eight gave it a top speed approaching 110mph (177km/h) which was matched by servo-assisted hydraulic braking. Its performance potential was such that Mercedes-Benz in the UK retained racing driver Goffredo 'Freddy' Zehender as technical adviser and demonstration driver, since the super-charged Mercedes was one of the few genuine 100mph road cars available in the 1930s.
Tested by Britain's Motor magazine, the 540K was judged to have less heavy steering and handling than its predecessor, the 500K, plus an even more comfortable ride, even though the same all-round independent suspension layout with parallel links and coil springs at the front and swing axles at the rear was retained. The Motor's test car returned 102mph over the timed quarter-mile with the supercharger engaged and 85mph with it disengaged. The servo-assisted brakes came in for fulsome praise, the blower was found to be relatively quiet and the springing more comfortable than that of the 500K, while the steering and handling also compared favourably with that model.
In May 1938, the 540K was tested by Motor's rival magazine Autocar and achieved the highest maximum speed of any road-test car up to that date: carrying three pas-sengers, the car reached 104.65mph (168.5km/h) on the race circuit at Brooklands, Surrey. 'One's foot goes hard down, and an almost demonical howl comes in,' reported test driver H S Linfield. 'The rev counter and speedometer needles leap round their dials: there is perhaps no other car noise in the world so distinctive as that produced by the Mercedes supercharger.' Late in 1938, a revised 540K made its appearance, with oval-section chassis tubes instead of channel frame members, while the adoption of sodium-cooled valves followed the company's highly success¬ful racing practice. The manufacturing record of the 540K reveals its exclusive nature: 97 being produced in 1936, 145 in 1937, 95 in 1938 and 69 in 1939 before the war ended series production (though three more were built up to July 1942). In recent years, the rarity, style and performance of these big supercharged Mercedes have made them one of the most sought-after of all classic cars on the few occasions they have come on the open market. Built to commission number '247491', the 540K offered here was delivered in July 1937 to Messrs Souheur & Chappuis, a Mercedes-Benz dealership in Brussels, for a Baron de Montpellier. According to the factory records the official designation of the body was two-door sedan, although it resembles a coupé in some ways. Irrespective of the designation this was one of the rarer body styles on the 540K chassis. According to the official body production figures, only 28 were built (presumably by Mercedes-Benz's in-house coachbuilder, Sindelfingen). Bonhams is grateful to Mercedes-Benz for providing the foregoing information from the factory records, which sadly contain no documentation concerning what happened to the car after delivery. At time of cataloguing no further information was to hand concerning its current mechanical condition or subsequent history.
Apparently an older restoration, '169341' is finished in dark midnight blue with dark sandy beige cloth interior trim. The dashboard boasts a full complement of instruments while other noteworthy features include twin side-mounted spare wheels, Bosch headlamps, centre spotlight, air horns and side exit exhausts. The supercharger is in place beneath the bonnet. Offering four-seater accommodation allied to breathtaking performance, this rare and stylish 540K coupé represents the very best that money could buy in the late 1930s and is a fine example of this classic German model.