The Nazis stripped hundreds of thousands of artworks from Jews during World War II in one of the biggest cultural raids in history, often photographing their spoils and meticulously cataloguing them on typewritten index cards.
Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday to search a free historical database of more than 20,000 art objects stolen in Germany-occupied France and Belgium from 1940 to 1944, including paintings by Claude Monet and Marc Chagall.
The database is a joint project of the New York-based Conference of Jewish Material Claims Against Germany and the United States Holocaust Memorial Museum in Washington, D.C.
The database is unusual because it has been built around Nazi-era records that were digitized and rendered searchable, showing what was seized and from whom, along with data on restitution or repatriation and photographs taken of the seized objects, the groups told The Associated Press.
The Claims Conference, which helps Holocaust survivors and their relatives to reclaim property, said it had used the database to estimate that nearly half of the objects may never have been returned to their rightful owners or their descendants or their country of origin.
"Most people think or thought that most of these items were repatriated or restituted," said Wesley A. Fisher, director of research at the Claims Conference. "It isn't true. Over half of them were never repatriated. That in itself is rather interesting historically."
Marc Masurovsky, the project's director at the museum, said the database was designed to evolve as new information is gathered. "I hope that the families do consult it and tell us what is right and what is wrong with it," he added.
The database combines records from the U.S. National Archives in College Park, Md.; the German Bundesarchiv, the federal archive in Koblenz; and repatriation and restitution records held by the French government.
By giving a new view of looted art, the database could raise questions about the possibly tainted history of works of art in some of the world's most important museum collections, experts said.
"I always tell people we have no idea how much is out there because nobody has ever bothered to take a complete inventory," said Willi Korte, one of the most prominent independent provenance researchers of looted Nazi art. "I think all of those that say there's not much left to do certainly should think twice."
Korte has been at the forefront of the worldwide search for art looted by the Nazis, an undertaking that has accelerated over the past two decades, spurring court battles and pitting the descendants of Jewish families who were forced to give up their possession against museums and private collectors.
Among the works listed in the database is a painting by the Danish artist Philips Wouwerman, which had belonged to the Rothschilds family and was discovered in the secret Zurich vault of Reich art dealer Bruno Lohse in 2007.
Korte, who was asked to develop an inventory of the works in the Lohse vault, said the Wouwerman painting "was clearly plundered."
No one knows exactly how many objects the Nazis looted and how many may still be missing.
The Claims Conference says about 650,000 art objects were taken, and thousands of items are still lost.
But the true number may never be known because of lack of documentation, the passage of time and the absence of a central arbitration body.
Some museum organizations have argued in recent years that most looted art has been identified as researchers focus on the provenance of art objects.
The database includes only a slice of the records generated by the Einsatzstab Reichsleiter Rosenberg, an undertaking of Third Reich ideologue Alfred Rosenberg to seize archives, books, art, Judaica, home furnishings and other objects from Jewish families, bookstores and collections. Records of the looting were disbursed to nearly a dozen countries after the war.
The database is focused on ERR spoils shipped to a prewar museum near the Louvre, where they were often catalogued and sold back to the market, destroyed or integrated into the lavish private collections of top Nazi officials — including the military chief Hermann Goering.
Julius Berman, the chairman of the Claims Conference, said organizing Nazi art-looting records was a key step to righting an injustice.
"It is now the responsibility of museums, art dealers and auction houses to check their holdings against these records to determine whether they might be in possession of art stolen from Holocaust victims," he said.
Database of Art Objects at the Jeu de Paume: http://www.errproject.org/jeudepaume