Thanks Guys for the information provided.
In July 2000 (before 9-11) I went to Mona Island for 5 days.I set my tent in Sardinera beach. I met with one of the Biologist on duty, he told me there is a Cave on the west side of the island which a "Fat Guy" tried to get permission to treasure hunting inside the cave because in that cave an Archaeolgist found two skull many years ago, but the permission was rejected.
The next day I went to the cave to take a video footage, not to metal detecting, only video.I didn't see nothig but rocks, old bottle and old wood stick. Three month later I watch the video again I noted inside the cave, right in one of many walls there is a carved signal with the number "12"(carved not graffiti). Will be a treasure signal?