Classic Cold War spy stuff here with a cool numismatic connection. How a Nickel and a Paperboy Brought Down A Cold War Spy
Then there were the Canadian spy quarters: Espionage warnings from the (US) Defense Department caused an international sensation a few years ago over reports of mysterious coins with radio frequency transmitters, until they were debunked. The culprit turned out to be a commemorative quarter in Canada. http://www.cbsnews.com/2100-250_162-5877951.html