The "great race car mystery" has now been solved.

Christie's, the auctioneers who withdrew the 1939 Auto Union D Type V12 Grand Prix Racing car originally scheduled for sale at Retromobile in Paris on February 17, has announced that after investigation and verification by Audi Tradition the car's chassis is frame 19, not 21 as originally thought. However Audi has confirmed that it is a genuine 1939 D Type chassis first raced by Rudolf Hasse in the Eifelrennen on the 20th May 1939 at the Nurburgring, in which Hasse finished in 5th place. It was next raced at the 1939 French Grand Prix in the hands of legendary Auto Union pilot Hans Stuck, who brought the car home in 6th place.

The D-type had a number of features that were extremely advanced, including an engine mounted behind the driver and four-wheel independent suspension. Its twin-supercharged 3-liter V12 can produce 485 horsepower, for a top speed of 185 miles per hour. Chassis 19 is one of only five still in existence.

Christie's is accepting sealed tender bids for a period from one week today, February 28. Prospective bidders are invited to contact its London office at +44 (0)20 7839 9060 to receive applications for this tender. If you plan on bidding, better make sure there's at least $13 million in petty cash; earlier estimates of the selling price were in excess of $12 million. If that seems a bit much consider that the Auto Union D-Type, designed by Professor Ferdinand Porsche, is historically one of motorsport's most important race cars. Thanks to Nigel for the heads-up on this one.