In 2008, the U.S. National Archives published The Mauthausen Concentration Camp Complex: World War II and Postwar Records, researched and written by archivist Amy Schmidt and intern Gudrun Loehrer; it's essentially a guide to all the records on Mauthausen held at the U.S. National Archives at College Park, Maryland.
Browsing through the guide, I was startled to learn the following (p. 51):Items cited as enclosures but missing from the Taylor Report
A 1943 “protocol” signed by Mauthausen Commandant Ziereis and Georg Bachmayer converting a police wagon into a mobile gas chamber.The American Lt. Jack Taylor was an officer in the Office of Strategic Services who was held prisoner at Mauthausen for little more than a month before it was liberated by his countrymen in May 1945. Taylor had been captured by the Germans working with partisans after he'd been parachuted-in behind enemy lines, and was therefore treated as a political prisoner opposed to a typical prison of war. Following liberation Taylor turned his skills to compiling evidence of German atrocities at the Mauthausen-Gusen concentration camps and sub-camps; more about Taylor's report can be read on the NARA guide linked above by searching for his name.
A protocol signed by a camp commandant and one of his senior men about converting an old police van into a homicidal gas chamber on wheels would certainly be of use to orthodox historians, so it is indeed unfortunate for them that it went missing. Assuming of course that the document was not an embarrassingly crude forgery, which it almost certainly was; it can easily be shown that there were some truly absurd claims being made by War Crimes investigators at Mauthausen about gas vans.
The following is an excerpt from Nuremberg documents PS-499, a report on the killing of inmates at Mauthausen concentration camp which declared that a gas van operated at Mauthausen in which Zyklon B was the deadly agent used to kill its passengers. No promoter of the claim that the Nazis operated homicidal gas vans today insists that anything other than the exhaust fumes of the vans' engines were used to kill the victims. This excerpt of PS-499 was also quoted (NMT:5, p.1137f) by American judge Michael A. Musmanno in his Concurring Opinion on the judgment of the 4th Nuremberg Military Tribunal, the "Pohl Trial":