Germany’s Kunstsammlung NRW has called on the panel of experts from the so-called Limbach Commission to adjudicate a long-standing restitution dispute between the museum and the heirs of the Jewish art dealer Alfred Flechtheim, Die Welt reports. The commission’s rulings are officially non-binding, but can hold significant sway in deciding restitution cases.

The museum claims that after years of provenance research it has not found evidence that proves beyond a reasonable doubt that Juan Gris’s Guitar and Ink Bottle on a Table (1913) belonged to Flechtheim. The museum’s research suggests that the disputed painting may have been on consignment or jointly owned by several gallerists when it was sold to a London collector in 1934. The heirs believe the sale was conducted under the threat of Nazi persecution.

In the past, the Flechtheim heirs have successfully reclaimed a number of artworks based on the commission’s recommendations. In 2013, the city of Cologne restituted Oskar Kokoschka’s Portrait Tilla Durieux (1910) to his heirs. The Kunstmuseum Bonn previously negotiated a compensation package with the family to keep a painting by German expressionist Paul Adolf Seehaus.

Alfred Flechtheim was one of the Weimar Republic’s most successful art dealers. He fled to London to escape Nazi persecution in 1933 and died in poverty in 1937.