The German car is described by Worldwide Auctioneers, who will be selling it in Scottsdale, Arizona, as “the most historically significant automobile ever offered for public sale.”

No official estimate has been given but Worldwide Auctioneers noted that its 2004 sale, as part of a wider package of Mercedes vehicles, marked the single most valuable private transaction in the classic car world at the time. The auctioneer said 10 per cent of Wednesday’s sale price will be donated to funding education about the Holocaust.

According to supporting documentation, the car was a product of design requirements laid down by Hitler and his primary chauffer, SS Officer Erich Kempka.

Kempka asked Mercedes engineers to ensure maximum protection for Hitler, even allowing for the fact that the car was an open tourer.

Built-in security measures applied to the vehicle included 30-millimetre bullet-resistant laminated glass for the fixed windscreen and detachable side panels. Armour plating protected the body sides and undercarriage while a further panel at the rear could be raised or lowered depending upon threat level.

Documents suggest the car was first used publically in October 1939 as part of a large motorcade delivering Hitler to the Old Reich Chancellery in Berlin in front of international media.

It was also used for a state visit by Italian fascist dictator Benito Mussolini in June 1940. Just one month later, Hitler used it for a victory parade after the Nazi’s swift defeat of neighbouring France. Further outings were made with Hitler as a celebrated passenger after German victories over Yugoslavia and Greece.

But as the war turned against Germany, the car was used much less and its latter wartime service remains unknown.

After Germany’s capitulation in 1945, the car was seized by American forces and used by U.S. Army Military Police stationed in Le Havre, northern France.

It was shipped to the United States in 1946, where it was bought by Tom Austin, a rich tobacco planter from Greeneville, Tennessee.

After falling into disuse, with apparently little understanding of its provenance, the car was eventually recognised and restored by two classic car hunters in 1976 before being sold on to Ralph Engelstad, owner of the Imperial Palace Casino and Hotel in Las Vegas.

At the time, it had an odometer reading of just 33,309 kilometres and auctioneers claimed it has only added 50 kilometres over the subsequent 40 years.

The auction begins at 5 p.m. local time Wednesday in Scottsdale.