Mysteriously, none of Duchamp's earliest originals has survived. All that remain are various photographs of the objects in his studio and later reproductions of the items, including sets authorized and signed by the artist and miniature versions made for Duchamp's "La Boîte-en-valise," or the box in a suitcase--a portable museum of his artworks.

Shearer suspects that Duchamp's original readymades, rather than being off-the-shelf, store-bought items, were all unique creations, extensively manipulated by the artist's hand. The assumption that a readymade is an unchanged everyday object is false, she says.

In fact, Duchamp himself had described some of the objects, such as the paint sign, as assisted or rectified readymades. The question is whether that was true for all the readymades.

One way to check would be to find other examples of those mass-produced articles that he claimed to have purchased or, at least, images of them in catalogs.

Shearer and Gould have assembled an extensive collection of antique hat racks, coat hooks, snow shovels, paint signs, perfume containers, and other items. "It was impossible to find exact replicas of the objects Duchamp claimed to have purchased," Shearer says, nor did they turn up in catalogs.

Another approach would be to take a close look at the photographs of Duchamp's originals, some made by the famed photographers Man Ray and Alfred Steiglitz. Careful analysis of the pictures shows that some of these supposedly mass-produced items have implausible features, Shearer says.