A rusty old Porsche which doesn't work has been described as one of the most exciting discoveries in recent years - and it is set to sell for £500,000.

The Porsche 356A 1500 GS Carrera Coupe helped bridge the gap between the company's sports vehicles and racing cars when it debuted in 1955.

But this 1957 model hasn't been driven for 45 years after its brakes failed a safety inspection in Georgia in the early 1970s.

The Porsche 356A 1500 GS Carrera Coupe was discovered in a barn in the United States where it has languished for 45 years

The 60-year-old sports car rolled off the production line in 1957 before it was exported to the United States

Since leaving Stuttgart, the rare sports car has declined dramatically having spent almost half a century in a shed

Its original engine was removed and taken apart and, after the best part of half-a-century of neglect, the bodywork and wheels are covered in rust.

However, as one of the most desirable classic Porsches there is no shortage of interest from around the world in the unrestored sports car.

They have given it a guide price of £500,000 ahead of its sale on March 9 at Amelia Island, Florida.

David Brynan, Gooding & Company senior specialist and Porsche expert, said: 'This was Porsche's top of the line road car and one of the most exotic sports cars of the 1950s.

The 1,500 cc aircooled engine, was cooled by a large fan, right, has been stripped from the vehicle 

The car still has its original four-cylinder engine which is ready to be reconditioned having been cleaned 

Inside the cabin, there are also signs of rust on the metal dashboard as well as cracks on the bakelite steering wheel

'They have always been sought after, so most have been restored at least once.

'To find a car that hasn't been seen in 40 years, and that retains so much original character is virtually unheard of.'

The car is being sold with the original engine, which will need to be rebuilt.

When in working order, the 1.5-litre engine will develop 100bhp - giving it a 0-60mph time of 8.7 seconds and a top speed of 125mph.

According to factory records, the 1500 GS Coupe was completed on July 4, 1957, and finished in silver metallic with black leatherette upholstery.

When it rolled off the production line, the car, pictured, was capable of travelling at 125mph

The original leather seats are still in the vehicle, although they will need work to return the car to concours standard

Despite the poor state of the body work, the car is still expected to sell for more than £500,000 when it is auctioned 

The dashboard has a badge celebrating the Deutsche sportswagen meister schaften - German sports car championships

It had numerous owners until 1973 when it was parked up in a garage and left for decades

The interior appears original and generally well-preserved and, despite being 60 years old, is thought to have been driven just 52,837 miles.

The auction house added: 'Hidden away for decades and possessing a fantastic history, this unrestored, matching-numbers 1500 GS Carrera is certainly one of the most exciting barn-find discoveries in recent memory.

'This is truly an opportunity not to be missed for the collector who has longed to own a genuine and noteworthy example of Porsche's legendary four cam.' 

The new owner can expect to spend a further £80,000 if they wish to return the car to concours quality 

If fully refurbished, the car, pictured, could be worth in excess of £750,000 

The car, pictured, was found abandoned in a barn having failed a safety inspection in the early 1970s

The car has its original identification numbers as well as its original engine - increasing its value considerably

The chrome on the car has become pitted with rush while the paint has peeled away leaving behind surface rust

The front of the car contains the fuel tank and the luggage space while the engine is placed in the rear

The car passed through several hands until it was parked up in the early 1970s having failed a safety inspection

The air-cooled flat-four engine developed 100 bhp at 6,200 rpm which could push the car to 60mph in less than nine seconds

It is clear from its shape, that Porsche designers used the 356A as inspiration a decade later when creating the iconic 911