The Star (h/t NonnyMouse):

An odd-looking Canadian coin with a bright red flower was the culprit behind the U.S. Defence Department's false espionage warning earlier this year, the Associated Press has learned.

The odd-looking - but harmless - "poppy coin" was so unfamiliar to suspicious U.S. Army contractors travelling in Canada that they filed confidential espionage accounts about them. The worried contractors described the coins as "anomalous" and "filled with something man-made that looked like nano-technology," according to once-classified U.S. government reports and e-mails obtained by the AP.

The supposed nano-technology actually was a conventional protective coating the Royal Canadian Mint applied to prevent the poppy's red color from rubbing off. The mint produced nearly 30 million such quarters in 2004 commemorating Canada's 117,000 war dead.