Only 17 Porsche 924 Carrera GTRs were ever built. This is one of them, and it’s coming up for auction at Silverstone Auctions’ classic sale. The estimated price? Um, over half a million pounds.

But wait: before you scuttle off, allow us to present some details. Details like its practically untouched 2.0-litre turbocharged engine that has covered less than 68 miles since 1981 (yes, sixty-eight miles).

Or its 375bhp. Or its 930kg weight. Or the fact it could go from 0-60mph in 4.7secs and top out at 180mph. Oh, and the fact 924 GTRs raced at Le Mans. Always good pub chat fodder.

Delivered new to Japan in 1981, it’s one of only two cars delivered to the country – the other one was reportedly used ‘extensively’ for racing. This one, not so much.

It was stored for two years, and then in 1983 sold to a classic car enthusiast who only took it out for very special occasions. Occasions like trackdays at Suzuka and Fuji. And each time, the owner would make a record of how many miles it had covered.

He clearly didn’t put in many laps, for after 68 miles, he packed the 924 away into a two-storey garage, accessible only by a lift. It was then removed every year to be serviced, and then tucked safely away from the harms of the world.

It’s so original, even the initials of the Porsche factory race technicians are still visible on the engine management box, along with handwritten stickers on the wiring loom and bits written in marker pen. All from 1981. Talk about a history lesson.

Ah yes, history. “It’s the 40th anniversary of the Porsche 924 this year,” explains Silverstone Auctions’ Nick Whale. “It’s a very special collectors’ item that would be the icing on the cake to any serious Porsche collection,” he adds.

In 1981, this GTR – surely fabled nomenclature, no? – would have set you back $75,000. Today, this rare example is expected to fetch anywhere between £475k and £575k. You can pick up a standard 924 for as little as £3,000, but that won’t be as cared for, as exciting, or with such strong motorsport heritage… Enough to make this GTR worth the outlay?