The art dealing firm of D. Katz was established in Dieren by Daniël Katz. Daniël had two sons, Benjamin (b. 1891) and Nathan (b. 1893); Nathan followed his father into the trade. In 1940 he established branches of the firm in Switzerland and in The Hague. Nathan Katz is known to have sold to German buyers, including Hermann Goering, during the occupation of The Netherlands by Germany during World War II. Katz was Jewish, but able to survive in Holland due to his connections on the art market through which he was able to procure paintings for the Germans. As part of his dealings, he managed to obtain a visa to Switzerland, where he went in late 1941 and remained for the duration of the war (in Basel). Katz traded pictures to Germans for visas for other members of his family as well. He died in 1949 in Switzerland, and two estate sales of his collection were held at the Galerie Charpentier in Paris in 1950 and 1951.
Venema, Adriaan. Kunsthandel in Nederland, 1940-1945. Amsterdam, c. 1986: 254-266
Nicholas, Lynn H. The Rape of Europa. New York, 1994:108-109.