It is part of a long-running campaign by the heirs for return of the so-called Welfenschatz, or Guelph Treasure – which they claim their ancestors sold under Nazi pressure and is worth an estimated $226m.
Originally collected over centuries by the Braunschweig Cathedral, the Welfenschatz includes some of the outstanding goldsmith works of the Middle Ages, among them ornate containers in the form of cathedrals used to store Christian relics.
Many of the silver and gold pieces are decorated with jewels and pearls. Some are more than 800 years old.
Lawyer Nicholas O’Donnell told The Associated Press in an interview in Berlin that the suit asks the Washington court to declare an American and a British descendant of a consortium that owned the collection in 1935 – when it was sold to the German state of Prussia – the rightful owners today.
“Any transaction in 1935, where the sellers on the one side were Jews and the buyer on the other side was the Nazi state itself is by definition a void transaction,” he said.
The organisation that oversees Berlin’s museums, the Prussian Cultural Heritage Foundation, says that the collectors were not forced to sell the pieces, arguing among other things that the collection was not even in Germany at the time of its sale.
Last year, a German government commission created to help resolve restitution claims evaluated both arguments and recommended that the collection stay in Germany. The commission wrote that after thoroughly investigating the sale process, it came to the conclusion that it was not a “forced sale due to persecution”.
The commission’s recommendations are not binding, but they are often accepted by parties in such disputes.
The foundation’s president, Herrmann Parzinger, said he was “astonished” by the claimants’ decision to sue for the collection.