LONDON.- A 1934 Mercedes-Benz 500 K special roadster, a unique variation of Mercedes-Benz top of the line 1930s luxury sports car, has been generously donated to benefit the causes of both the Swedish Cancer Society and The Swedish Alzheimer's Foundation charities.

Offered at no reserve with an estimate of €3.6 million (circa £2.9m / $4.8m), it is set to be a highlight of the Bonhams auction which takes place at the Mercedes-Benz Museum in Stuttgart, on 12th July, 2014.

Built precisely 80 years ago, the car was a one off version of the company's most exclusive and expensive 1930s models. It boasted an eight-cylinder supercharged engine that could propel the car to 160kph. Its exclusive coachwork was a variation of a production design which was accented by additional chrome trim 'sweeps' on its wings, a 'waterfall' radiator grille cover and chrome covers to its twin spare wheels at the rear. As new, the car was appropriately finished in a colour named 'speedgray'. When the 500K model was upgraded to the 540K it was returned to the factory to receive the improved larger 5.4-litre engine and the aesthetic improvements of these later models.

Discovered by a Scandinavian enthusiast in the 1970s it was fastidiously restored to its former glory and remained within single ownership for 40 years until its donation to the charities this year.

“This generous donation will help us get closer to achieving our vision of conquering cancer”, said Stefan Bergh, Secretary-General of the Swedish Cancer Society.

“The proceeds from the sale of this rare vehicle will benefit all those affected by cancer by contributing to the funding of important scientific research.

“The Swedish Cancer Society annually funds approximately 450 research projects. To do this, we are entirely dependent on the generosity of private donors. We are very grateful for their support, as their gifts enable much of the ground-breaking work being done by Swedish scientists every day.

Liselotte Jansson, Secretary-General of The Swedish Alzheimer's Foundation concurred, “We are utterly grateful for this generous donation which will help us reach our goal of finding a cure for Alzheimer’s, which is the most common form of dementia.

“Dementia is today classified as a common disease, with the number of people suffering from it expected to double every 20 years. Intensified research in this area is therefore crucial in order to find a cure.

“The Swedish Alzheimer's foundation is a small but rapidly growing foundation, and the largest contributor to Alzheimer’s research in Sweden. The donation will enable us to support new innovative research and coming one step closer to our vision of a world free from dementia.”

The Mercedes-Benz Museum maps the entire history of the world’s oldest car manufacturer with a unique variety of exhibits. A total of 1500 exhibits, including 160 vehicles, can be seen on an area of 16,500 square metres.