We're used to seeing original Shelby Cobras head to auction and ultimately sell for a lot of money, but this particular Cobra is a bit different from the others. Set to cross the stage at RM Auction's Arizona auction next month is this 1966 Shelby 427 Cobra Semi-Competition. What is 'Semi-Competition'? It was intended to be a race car, like the rest of the 427s, but Shelby didn't build enough examples in time for homologation when FIA inspectors came to his facility. Subsequently, Shelby was denied FIA approval.

He then canceled his order for the remaining competition cars, of which just 53 were produced. Of those, 16 were sold to private teams, two were retained as prototypes, and one sent to Ford Engineering. The remaining competition chassis were painted and turned into street cars. Shelby marketed them as the 427 S/C, or 'Semi-Competition.' The 427 V8 had a then insane 500 hp and only a guy like Carroll Shelby could come up with the idea to swap out the 289 in favor of the larger V8. But he did, and the result was the fastest road-going car ever built at the time. It retained the oil cooler, riveted hood scoop, flared fenders, side exhausts, 42-gallon fuel tank, and external fuel filter of the full competition models.

Let's just say these 427 S/Cs were brutally fast and immediately became known as the ultimate Cobra. This 427 S/C, chassis number CSX 3040, has had four previous owners, all of whom took excellent care of it. It even spent 20 years in Australia where one owner lived, but returned to the US in 2001 when its current owner took possession. It was this owner, renowned Cobra expert Mike McCluskey, who performed a full restoration. He determined, when he took the car a part, that all of its body panels, engine, drivetrain, interior, and accessories were all original. There was very little damage after years of use. All of the original instrumentation was retained during the restoration, and the engine was rebuilt and tested.

The sale includes a copy of the original sales invoice. This Shelby 427 Cobra S/C is about the best you can buy if you're a Shelby collector. Speaking of which, RM Auctions estimates it'll fetch between $2 million and $2.4 million. Photos courtesy of Patrick Ernzen/RM Sotheby's.