You may or may not be familiar with "milagros" which are miracle charms in hispanic culture.
Basically, they relate to a specific prayer request and you wear them for good luck or to receive a miracle.
When I was in Greece, I remember something similar there, except it looked more like a dog tag with an icon (related to the miracle) stamped onto it. I could be misremembering, but I actually thought that these charms were used to commemorate a loved one who had died from some ailment instead of to request intervention. So, if someone had died of lung cancer, the dog tag would have lungs on it. Does anyone have any clue of what these are called?