Customs officers at Sofia Airport blocked an attempt to smuggle 82 silver coins believed to date from the time of the fourth century BCE king Philip II of Macedon, the Customs Agency said.
Some of the tetradrachm coins were carved with the image of the king with a crowned head, dating from 359-336 BCE.
Experts said that the coins were of outstanding cultural value, the agency said. All were protected under the Cultural Heritage Act.
Apart from their high monetary value, the coins were of extremely high historical value.
The coins were hidden in three routers and were to have been taken from Bulgaria to the United States. Investigations were continuing, the agency said.