A 1931 Bugatti type 51 grand prix racing two-seater has sold for $4m at Bonhams - a record for the model.
It was the headline lot of the August 19 Quail Lodge auction.
The model represented a major step up from the previous generation in terms of its speed and handling on the track.
The auction house explained the car's enduring appeal: "As ever with Bugatti, the aesthetics in every form compliment the incredible power of this American-inspired, Franco-Italian supercharged 2.3-litre twin-cam racecar.
"The result is a highly dynamic and potent sculpture of beauty capable of producing 160hp and a speed of 130mph.
"Never publicly offered for sale, in the present ownership for more than 30 years, unseen publicly for more than 20 years, and with just two owners since the 1950s, this Bugatti is one of the finest examples in existence."
The car's rich racing history was also a draw.
It was competed across Europe by Tazio Nuvolari and Lord Howe during the 1930s - achieving a notable fourth place at the Monaco Grand Prix in 1932.
The lot was joined by an extraordinary compliment of performance cars that spanned the past century, including a 2014 Ferrari LaFerrari that made $3.6m.
The model was unveiled at the Geneva Salon in 2013 and sold out immediately. Only 499 were ever made.
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