The discovery of a barn find — an unmolested vehicle of value that comes to light when the detritus of an old shed or warehouse is pushed aside — generates great excitement in the collecting world. And in the view of many, so much the better if the car is covered with layers of crud; some owners are reluctant to clean their discoveries. But preservationists are very clear on this point: dirt is corrosive, so it should be removed as soon as possible. Like fine art, cars should be clean.

In his book, Dr. Simeone discusses the concept of material truth, that the historical relevance of a preserved object derives from its actual physical materials. If you stand before the larger-than-life statue of David in the Galleria dell’Accademia in Florence, you know it was created by Michelangelo’s hands and it may make you feel different than if you were viewing a replica.

In the same spirit, a good replica of a Shelby Cobra may perform better than the original, but Carroll Shelby didn’t build it or bless it.

A program at Stanford University called Revs is analyzing the materials in classic cars and the effects of compounds ranging from sweat and skin oil to wax and acid rain. Founded by Miles Collier, a noted collector and preservationist, the multidiscipline Revs curriculum also explores the full spectrum of human interaction with the car. As expected, the Revs faculty has mechanical engineers, but it also includes archaeologists, lawyers, artists and human behaviorists. In one course, subjects are connected to sensors and monitored by cameras as they drive classic cars and futuristic new cars. In another, a classic car is literally restored during the semester using preservation techniques.

On average, automotive tastes are maturing, and without twisting anyone’s arm or wallet, unmolested cars are becoming more important in the collecting world, especially those in the one-of-a-handful category. A good example is the Simeone Museum’s Daytona Coupe — a sleeker, enclosed version of the legendary Shelby Cobra. It was built in the 1960s for the high-speed straights of Le Mans, to topple the Europeans’ domination of the 24-hour race (which it did). Only six Daytona Coupes were made, and years ago five of them were fully restored, erasing some of their unique history. The museum’s Daytona Coupe is the only one still wearing its original paint, so it also serves as an invaluable reference vehicle.

While none of the 60-plus cars in the museum are for sale, the Bonhams auction includes vehicles ranging from a 1924 Ford Model T 5-Window Coupe, with a presale estimated price of only $10,000 to $15,000, to a 1973 Ferrari 365 GTB/4 in the $340,000 to $380,000 range. Also offered is a 1932 Aston Martin 1 1/2-liter Le Mans 2-4 Seater. Designed to be driven to a race, win and drive home, the Aston was once owned by the British film director Basil Dean. Another original car, a 1931 Isotta Fraschini Tipo 8A two-door faux cabriolet, with coachwork by Lancefield, recently emerged from storage in Connecticut after 37 years.

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Bonhams’s “Preserving the Automobile” auction will be Oct. 8 at the Simeone Foundation Automotive Museum, 6825 Norwitch Drive, Philadelphia, simeonemuseum.org. Automobilia goes on sale at 10 a.m. and cars at 2 p.m. Admission is by $30 catalog, which admits two people to the museum and the auction. Vehicle information at bonhams.com.