An ancient Egyptian mummy mask made of gold and dating back to between 1307 to 1196 B.C. is at the center of a bitter antiquities dispute between St. Louis and Egypt, the Associated Press reports via the International Herald Tribune.

The mask was discovered in 1952 by Egyptian archaeologist Mohammed Zakarais Ghoneim at the Saqqara pyramids. Ghoneim placed the relic in the government warehouse at Saqqara at the time, documenting his discovery and storage of the piece in the warehouse's ledger. In 1957, he published his discovery in a book, and in 1959, according to another record from the Saqqara warehouse, the mask was packed in a box with other antiquities for a shipment to the Egyptian Museum in Cairo.

There are no further documents tracking the movements of the mask; it resurfaced in 1998, when the St. Louis Art Museum acquired it. Egyptian research has concluded that it was stolen in 1959, most likely from the Egyptian Museum or en route there from Saqqara. But the country only reported it stolen in 2006 and did not file a claim with the Art Loss Registry.

The St. Louis museum says that it checked with the registry before purchasing the mask. It also claims that it sent a letter to the Egyptian Museum notifying it of the acquisition, and that the museum did not say that the artifact was stolen in its response.

According to the St. Louis museum's provenance for the piece, it was owned by a Belgian art dealer in 1952. But Egypt is accusing St. Louis of falsifying the provenance, citing its own records as contrary evidence.

Brent Benjamin, director of the St. Louis museum, said he is not opposed to returning the mask if Egypt can prove it was stolen. "To date, we have not seen information that we believe is compelling enough to return the object," he said. Zahi Hawass, head of Egypt's antiquities authority, has made this case a top priority, recently getting the U.S. Department of Homeland Security to begin looking into the situation.