Here in an CNN interview with Marianne Rosenberg, the granddaughter of art collector and dealer Paul Rosenberg, the New York art dealer says that she heard from Focus magazine that one of her grandfather's paintings may have been found. Ms. Rosenberg says that she remains "cautious" as "German authorities have said nothing." Last weekend the German magazine Focus published an article in which it claimed that a Matisse previously owned by Paul Rosenberg (Portrait of a Woman) had been found by Bavarian customs officials in 2011. Ms. Rosenberg explains that an archive is maintained of her grandfather's collection.

The Paul Rosenberg Archive describes the Parisian art dealer:

Paul Rosenberg's legendary 'stock' included a rich selection of paintings, drawings and sculptures by Géricault, Ingres, Delacroix, Courbet, Rodin, Cézanne, Manet, Degas, Monet, Renoir, and Lautrec, along with the works by his modern artists, and regularly complemented by works of Henri Rousseau, Aristide Maillol. Odilon Redon and Amedeo Modigliani. His 'stock' from artists in the United States included painting and sculpture by Marsden Hartley, Max Weber, Abraham Rattner, Karl Knaths, Harvey Weiss, Oronzio Maldarelli. Both Paul and his son Alexandre also had contracts with Nicolas de Staël and Graham Sutherland. Alexandre Rosenberg was the American representative and close friend of the sculptors Kenneth Armitage and Giacomo Manzù.

Paul Rosenberg opened a new branch of his Paris gallery - managed by his well-known antiquarian brother-in-law Jacques Helft - in London between World War I and World War II. From 1920 until the beginning of the Second World War in 1939, Paul Rosenberg's company was widely acknowledged to be without doubt the most active and influential gallery in the world in the field of 19th and 20th century French painting, specializing in the Impressionist, Post-Impressionist and Cubist schools, as well as in the developments contemporary to these 'schools'. All of the museums of the Western world and all of the great private collectors became clients of Rosenberg, and his exhibitions became points of reference for the promotion of quality painting.

Having foreseen the imminence of the Second World War, Paul Rosenberg began to send his collections abroad, especially to England, America, Australia and South America and then put a hold on the operations of his Paris galleries. Even prior to his departure from France with his wife and daughter, his many friends in the United States encouraged and assisted his establishment in New York, where the Rosenbergs arrived, via Lisbon, in September of 1940. Rosenberg presence in New York had attracted so much interest that an issue of the Art Digest declared that "When rumor first intimated that Paul Rosenberg, internationally known Paris dealer in modern art, would open a gallery in New York, 57th Street anticipated something akin to a clap of thunder." Throughout the war and after its end, he was able to re-assemble in New York a very large proportion, though not all of his gallery stock and his personal collections. In this way, and almost without interruption or discontinuity, he re-established his gallery in New York and recommenced the activity previously undertaken in Paris.

This New York Times article by Tom Mashberg recounts the negotiations over the provenance of a Matisse painting once owned by Paul Rosenberg and now on display in Oslo.