The Things Spies Hide in Coins

This is a general feature story on an exhibit but does mention two items that might be fun to research further, a poison pin hidden in a silver dollar and a coin containing microfilm.

Museum to Decipher Mystery Coin from a Garden

Should have an update on this one any day now, a coin found by a lady in her garden is being deciphered by a British museum. I can't make it out very well in the picture offered but sure looks like St. George and the Dragon, which would make the "pilgrimage" guess a good one.

Byzantine Gold Coin Clue to Shroud of Turin

You have to get down about halfway in the story to find the reference, a Byzantine gold coin bears an image comparable in many ways to the controversial Shroud of Turin image.