An odd but effective 20th Century Fox promotion for this summer’s Fantastic Four: Rise of the Silver Surfer has gotten the studio in trouble with the United States Mint:

The studio, 20th Century Fox, hired the Franklin Mint, a private company that manufactures scale models, statuettes, pocket knives, medallions and collectibles, to place a full-color image of the Silver Surfer, complete with Web address, on the backs of 40,000 California statehood quarters.

The altered coins (which are not in fact silver) were distributed nationwide in the period leading up to Memorial Day. Visitors to the Web site can compete to win a prize in connection with the movie’s June 15 release (finding one of the coins is not required).

But the United States Mint, which is the exclusive maker of American coinage, took exception to the stunt. Although it is not illegal to deface American coins as long as there is no intention to defraud, it is illegal to advertise on coins, the mint pointed out last week.

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