Joseph Duveen once sold an Albrecht Durer painting for several hundred thousand dollars to a noted New York collector. Some time later, Duveen was invited to the client's home where a fellow guest -- a young French art scholar -- was shown the new Durer by the client's daughter.

The man studied it for several minutes before whispering, "You know, I don't think this Durer is right." The girl promptly informed her father, who turned to Duveen.

"How very amusing," the dealer laughed. "Do you realize, young man, that at least twenty other art experts here and in Europe have been taken in too, and have said that painting isn't genuine? And now you've made the same mistake."

Such was his breezy confidence, that the young Frenchman was soon apologizing for his unfortunate "error".