Some of history's truly great automobiles have been born from engineers working off the clock, building experimental projects far from the prying eyes of company brass and the meddling of the accounting department. Especially within large companies, radical ideas will surely be nixed if merely presented on paper. One such engineer was Erich Waxenberger of Mercedes-Benz. In the late 1960s, Herr Waxenberger came up with the simple but elegant idea of the ultimate factory super sedan. Starting with a standard W109 sedan, a car that left the factory with nothing bigger than a 3-liter inline-six, and working on his own time, he shoehorned in the mighty 6.3 liter all-alloy M100 V8 into the mid-sized saloon. The M100 was designed specifically for the highly exclusive 600 sedan and limousine, but Waxenberger believed that not only could he build a superb sporting saloon using the smaller body, he could better utilize the specialized production facility that was building these massive engines. He and his team built a prototype and handed the keys over to Mercedes-Benz factory test driver Rudi Uhlenhaut. The legend is that Uhlenhaut had to stop and open the hood at the first traffic signal to see what on earth Waxenberger had crammed into the 300SEL! Buoyed by the enthusiasm from Uhlenhaut, the car saw rapid approval by company bosses, especially given that the expensive M100 engine could now be sold in another car. The production version of the 300SEL 6.3 featured sophisticated air suspension, a four-speed automatic transmission, four wheel disc brakes, electric windows, sunroof, opulent wood trim and leather upholstery. Upon its introduction to the public in 1968, it was declared the fastest four-door car in the world and could easily keep pace with American muscle cars of the era. In fact, the 300SEL 6.3 could give a contemporary Porsche 911 a serious run for its money. Road & Track magazine declared it "merely the greatest sedan in the world". While less expensive than the 600, the 6.3 was still a costly car when new, and just 6,500 were built between 1968 and 1972. The 6.3 served its purpose as a regular production outlet for the M100 V8, as well as forming the foundation of a legacy of high-performance luxury sedans that Mercedes-Benz still upholds with the AMG line of super saloons. This 1970 300SEL 6.3 is an attractive and understated example, finished in Light Ivory (code 670) over red leather upholstery (code 242). It is a very well-maintained and largely original car, accompanied by extensive service records from model specialists. The body is straight and clean, with an attractive, good quality respray over an excellent body. Gaps are factory precise and all four doors operate with that signature vault-like feel. The original bumpers, body moldings, grille, window surrounds and other brightwork are all straight and in good order, benefitting from a recent polish. It rides on a set of beautifully finished factory Bundt alloy wheels that lend a slightly aggressive and purposeful look to the otherwise restrained Paul Bracq-penned styling. This 6.3 is in many ways the ultimate sleeper: Understated, with only its discreet badging and a slightly wider stance giving the slightest hint at its massive acceleration and 140mph ability. Stepping into the luxurious cabin, you may still be hard pressed to realize this is a serious performance car. The atmosphere is very much about comfortable touring over outright sportiness, with high quality and attractive leather trim and wood moldings. The leather is believed to be original, and presents in very good condition, showing a slight bit of wear on the driver's outer bolster, but remaining attractive and supple with an inviting light patina. The rear seat is in similar condition, showing little use. Wool carpets are excellent as are the door panels and recently refreshed headlining. Beautifully restored wood trim adorns the dash fascia, dash top, as well as door and windscreen surrounds. It is also equipped with an original Becker Mexico cassette player and correct ivory steering wheel. Mechanically this car is in very sound order and is essentially turn-key and ready to enjoy. Records show the air suspension was fully rebuilt, as was the complex fuel injection pump; rebuilt by respected specialist Jerry Fairchild. The steering box was removed and resealed, and many bushings and ancillaries refreshed in the chassis. It works as it should and is a strong performing example, a very important factor when considering any 6.3. Included in the sale are original books, manuals and tool kit along with the extensive service records and factory service information. The 300 SEL 6.3 is a car that should never have existed in its day yet went on to become a legend, the father of a line of performance sedans that continue through today. This is a cherished example that has had thousands spent to ensure it continues to thrill drivers for years to come.