A 17th-century painting in the Metropolitan Museum’s collection may be Nazi loot.

A 17th-century painting in the Metropolitan Museum’s collection has come under scrutiny following a discovery that it may have been seized by the Nazis in 1933 after its owner, the Jewish art dealer Siegfried Aram, fled Germany. Joachim Peter, a photographer and researcher studying Heilbronn, a city where Aram lived, recently uncovered documents suggesting the dealer once owned the work in question, The Rape of Tamar (ca. 1640), attributed to the French painter Eustache Le Sueur.

The painting has been in the Metropolitan Museum’s collection since 1984, when the museum bought the work from a trio of dealers who’d purchased it at a Christie’s sale the year before, for £108,000 (about $485,000 in today’s dollars). According to an unnamed dealer cited by the New York Times, the painting may now be worth $1.5 million.

However, according to documents unearthed by Peter, the painting may have been seized by Oskar Sommer, a German department store owner who bought Aram’s house in the Black Forest in 1933. The art dealer had fled the country by then, leaving his mother to sell the family’s holdings. The painting had been promised to a buyer in California, but documents suggest that Sommer kept it.

None of these provenance issues were apparently known at the time of the 1983 auction or the Met’s 1984 acquisition. Yet the museum told the New York Times it has launched an investigation:

The Met recently won a court battle over a Nazi loot claim involving Pablo Picasso’s famous painting The Actor (1904–05). The claimant in that case, the descendant of German-Jewish art collectors who sold the painting for $12,000 as they fled the Nazis, is now petitioning the U.S. Supreme Court to hear her claim.