Consists of Ambruster's works, correspondence, miscellaneous material, and printed matter. The collection contains typed drafts and galley proofs of Treason's Peace (New York: The Beechurst Press, 1947), as well as articles, copies of statements delivered before the Senate Subcommittee on Trading with the Enemy Act, and notes regarding future works. Much of Ambruster's works and correspondence deal with his opposition to post-World War II reparations to Germany, the return of German assets vested by the United States during the war, and the return of the General Aniline and Film Corporation to I. G. Farben. The collection reflects his support during World War II of the Alien Property Custodian who was authorized to seize all patents controlled by the enemy and to make them freely available to American industry, as well as his opposition to the Committee for the Return of Confiscated Property after the war. In addition, there are clippings of articles Ambruster wrote for The Daily Compass and The New York Post Home News.