Mr. Bartlett purchased the Jaguar at a 1998 Christie’s auction, virtually untouched from new  a time capsule  and the only one of the 16 XKSS’s that had never been restored. The car, which was displayed at the 1957 Chicago Motor Show, had been all but given up for lost. In fact, it was hiding in plain sight, still in a garage, still in Chicago and in the hands of the second owner who had bought it in 1960.

Sloppy handwriting had resulted in the misreading of the owner’s last name and sent searchers on wild goose chases over the years. A dealer of rare cars, contacted by the second owner, took charge of the XKSS and consigned it to the Christie’s auction in London.

Externally, the car is exactly as it appeared in Chicago in 1957. The paint, the interior and even the tires, convertible top and top cover are original. Naturally, the car has a patina but it is utterly authentic and remarkably well preserved. Mr. Bartlett had the mechanical systems inspected and reconditioned as needed with original parts.

As a comparatively new pursuit, car collecting has yet to adopt the guidelines typically followed by collectors of other historic objects. Europeans have been a bit ahead of the curve on this; the mandate of the Fédération Internationale des Véhicules Anciens, founded in 1966 in France, is to identify and classify vintage vehicles of all types and to assist in sorting out the differences among vehicles that are original, reproductions or fakes. No equivalent organization exists in the United States.

Tom Cotter, co-director of the Amelia Island Concours d’Élégance, a major show held in Florida each March, said he thought the psychology of car collectors was somewhat different from that of other collectors. Cars are an expression of one’s personality, and “car collectors are often perfectionists who simply cannot resist putting their thumbprint on a car,” he said.