The most important racing car to hit the auction block in years will roll in front of bidders this July 12: Juan Manuel Fangio’s Grand Prix winning Mercedes-Benz W196 — after being "forgotten about" in a warehouse for 30 years.

The 2 1/2-litre straight-8, bearing chassis number "00006," won both the 1954 German and Swiss Formula One Grand Prix races at the hands of five-time World Champion Fangio, and stands to make an immaculate hallway decoration for the wealthy collector when the machine goes to auction at Bonhams' sale during the Goodwood Festival of Speed. And despite being nearly abandoned, it should fetch at least $7.5 million.

The W196 brought innovative technologies to Formula One such as a fuel-injected engine, fully independent suspension, all-round inboard-mounted brakes, and an inline (or lay-down) engine with the goal of creating a lower center of gravity. However, the original W196 Stromlinienwagen was produced with enclosed wheels, and despite finishing first and second in its first race, it was deemed too difficult to place at the more technical racetracks. Mercedes, taking Fangio’s critique to heart, created the open-wheel W196, numbered "00005" and "00006." Fangio took the "00006" to victory in its first attempt at the German Grand Prix.

This victory was then repeated at the following Grand Prix in Switzerland, where Fangio thrashed Ferrari driver Jose Frolian Gonzalez by 58.7 seconds. That win was Fangio’s third in four races, ensuring him his second of five Formula One World titles.

But somewhere along the way, the car fell off the map. According to Bonhams, about 30 years ago the owners tested the engine one last time, then stuck it in a warehouse, where it has sat until now, having never been restored since it raced. That only makes it more valuable; as racing historian Doug Nye told The Age: "Every car that's restored has lost a part of its history because it's been obliterated by repainting or by rebuilding. Nothing's been obliterated on this, it's just a beautiful survivor."

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Bonhams Chairman Robert Brooks, calls the "00006" W196 perhaps the “pinnacle” of his five-decade span auctioning off racecars. It is also the only W196 that doesn't still belong to Mercedes-Benz, which rarely sells bits of its racing history.

I’ll be intrigued to see who buys this amazing machine, and even more intrigued to hear what they plan to do with it; Bonhams hopes the buyer restores it enough to run next year on the 60th anniversary of Fangio's win — but not make it too perfect.

Photos: Bonhams/the Spitzley-Monkhouse Collection