From vague press release:

An ancient stone coffin and sculpture of a lion's head have been returned to Greece after being handed over by two private owners in the United States, the Culture Ministry said Wednesday.
The artifacts were presented by new Culture Minister Michalis Liapis, who was sworn in Wednesday, after his conservative party won a second term in national elections Sunday.
Both items were voluntarily turned over to the Greek consulate in the U.S. city of Boston and returned to Greece in late July.
The undated marble sarcophagus bears the relief sculpture of a battle scene, while the lion sculpture is dated to Roman times.
Greece has mounted an aggressive campaign in recent years for the return of ancient artifacts from museums and private collections abroad _ including legally and illegally acquired items.

The campaign is part of an effort to recover Parthenon sculptures _ the Elgin Marbles _ from the British Museum in London, arguing that they are an integral part of the temple on the Acropolis hill.
The marbles were removed by Britain's Lord Elgin in the early 19th century.