Descendants of Jewish art dealers who lived in pre-World War II Germany are suing the German government, claiming they are the rightful owners of a valuable collection of medieval relics that ended up in the hands of the Nazis.

The plaintiffs are seeking the return of the Welfenschatz, also known as the Guelph Treasure, a collection of several dozen medieval relics. According to a lawsuit filed on Monday in federal district court in Washington, the estimated value of the collection exceeds $250 million.

Nazi leaders orchestrated the sale of the Welfenschatz to the Prussian government in 1935, the plaintiffs claimed, forcing the consortium of Jewish art dealers who owned the collection to sell it under duress for far less money than it was worth. The collection was presented as a “surprise gift” to Adolph Hitler at a ceremony later that year, according to the complaint.