You aren't going to believe this story. It sounds like the movie "enemy of my state". A Canadian special coin the poppy coin which has red poppy center protect bed special paint that shines purple under UV light. Well, a US defense contractor thought that the Canadian government is spying on the US by implanting nano-technology into the coin to track the person who carries the it.
The story made news headline that cause major embarrassment to the US defense department. The Canadian CSIS was annoyed by the
contractor report. Everyone else, including the Mint, was laughing at the contractor report to the US government.

http://ca.news.yahoo.com/s/capress/us_cda_spy_coins