It MIGHT be part of a themed set of caches. For example in my area, the Sackville "S"crabble cache has scrabble pieces in it and the requirements to log the cache as a find is that you have to take a piece from that cache and place another cache in an area starting with that letter (eg. if I went there and pulled "H", then I'd have to place a cache in a place starting with H...like Halifax) most people will attach the scrabble piece to the cover as further proof that they were there.... hope this helped