One of California's great historical mysteries apparently has been solved by researchers who spent 11 years studying the origins of what is known as "Drake's Plate." According to legend, the inscribed brass plaque was left near San Francisco in 1579 by Sir Francis Drake when he claimed the Pacific coast for England.

The accounts of Drake's voyage state very clearly that Drake claimed what would become the United States with a plaque that he set up on a post at his landing place at Drake's Bay in Marin County. But as NPR's Andy Bowers reports, the plate was most likely an elaborate practical joke played by some eminent historians in the 1930s on one of their own.

Herbert Bolton, history professor at the University of California, Berkeley, had long been known for encouraging his students to look for the brass plate -- and in 1936, when a shop clerk brought a battered brass plate to his office, he thought he had found it.

"Bolton himself questioned it," says Edward von der Porten, who led the research project that proved the brass plate was a fake. "The trouble was, he wanted it to be real very badly. And he didn't question it hard enough."

Researchers now believe that members of a fun-loving history and drinking club called E. Clampus Vitus created the plate as a joke against Bolton, a member of the club. "And the search for Sir Francis Drake's real plate can now continue," Bowers says.

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