Fonds consists of material that documents his career as a writer and broadcaster and, as such, includes correspondence with publishers, fan mail, research material, newspaper clippings, reviews of his work, notes, drafts and galleys related to his novels and works of non-fiction. The writing files include photocopies of his own letters written to his mother when he was an internee in England and manuscript and photocopies of letters written to Koch from Daria Hambourg and used as research material for his novel, "The Brothers Hambourg". Fonds also includes transcripts of interviews as well as written reminiscences in the form of letters from many former German internees; these letters were subsequently used as resource material for his book "Deemed Suspect: A Wartime Blunder". Fonds includes a complete set of published copies of his books. The broadcasting files contain correspondence, memos, notes and drafts of scripts, scrapbooks and other material that documents his long career with the CBC.