The Getty Museum has returned three fragments of an ancient gravestone to Greece, following a deal made in 2011. Two of the fragments join onto another fragment that had never left Greece.
Greece plans to lend other artefacts to the Getty in return.
Archaeology News Network 
Getty Museum repatriates antiquities to Greece
Source: Associated Press [March 09, 2012]
Three ancient marble fragments from the collections of the J. Paul Getty Museum in Los Angeles have been repatriated to Greece following a deal last year.
A culture ministry statement says two of the 2,400-year-old pieces are parts of the same broken gravestone decorated with relief sculptures, and will be joined onto a third section in a Greek museum.
The Getty also returned an inscribed slab related to a religious festival. The 5th century B.C. fragments arrived in Athens Friday.
Greece is discussing lending an ancient Greek inscription to the Getty in return.
In recent years, the Getty has repatriated to Athens another four significant ancient works, including a gold wreath allegedly illegally excavated in northern Greece.
Most of the Greek antiquities displayed in museums worldwide are of uncertain provenance.