Gertrude Appelbaum (also known as Apple) worked in the theater as a casting and production assistant for various producers including Howard Lindsay, Russel Crouse and Guthrie McClintic. She was also a business manager for the Theatre Guild (1964-1965), and personal manager for various actors. In 1947 she formed an investment syndicate comprised of investors with small sums to invest in Broadway productions.
From the description of Gertrude Appelbaum papers, 1942-1973. (New York Public Library). WorldCat record id: 122580854
From the guide to the Gertrude Appelbaum papers, 1942-1973, (The New York Public Library. Billy Rose Theatre Division.)