Able to reach 100mph, the S-Type Mercedes Benz was among the world's fastest when it came off the production line in 1928.
And this model still runs perfectly, despite having last been used in the the 1950s.
Now the motor is set to go under the hammer at Bonhams’ Goodwood Revival sale on September 15.
Automotive expert, Rupert Banner, said: “At a time when motor cars in original condition and with impeccable provenance are appreciated more than ever, this one-owner car offers an unrepeatable opportunity for collectors.
“It has literally been off the radar. No one knew such an untouched and archaic this old existed. It is an incredible find.”
The unidentified owner's grandfather was one of the earliest buyers of the car, purchasing it from The British Mercedes Ltd in London.
A spokesman for Bonhams said: “This newly discovered 1928 Mercedes-Benz S-Type Sports Tourer is almost without precedent.
“Motor cars of this type and age have rarely been in the same family ownership from new.
“It is expected to sell for more than £1.5m.”Source