"The are conflicting stories as to the use of the [Dachau] gas chamber. An Albanian tells me that it was used only four times since 1942, but a Pole says that it was never used during that time. Another Pole reports that 100 or 150 people were put to death each day in the chamber. A Yugoslav says that thousands were gassed in the last three years. A Frenchman believes that the chamber has never been used."Lieutenant Marcus J. Smith, U.S. Army doctor, arrived at Dachau the day after liberation; later awarded the Bronze Star and promoted to Captain for his efforts in helping the sick at Dachau.
This is my April 13, 2014 photograph of a museum display in the Permanent Exhibition at the Dachau memorial, and below is a close up photograph of the image in the left centre of this display.
As you can see, it's a scan of an original May 23, 1942 construction plan of the new crematorium at Dachau which the museum insists contained a purpose built homicidal gas chamber, which, they presently claim, was only ever used on an experimental basis, although prior to 2003 they claimed it was never used at all.
I'm sure most of you won't need me to tell you that design features absolutely fundamental to the presently claimed gassing procedure are absence from this plan.
What the museum describes on signs in or around the crematorium as "[f]laps where prussic acid poison gas pellets (Zyklon B) could be inserted from the outside", do not feature on the original architectural plan of the building.
As is widely known (and detailed excellently here), the original claimed gassing method at Dachau—the one reported to the U.S. Congress on May 15, 1945 by Senator Alben W. Barkley, and the one described in the film shown at the Nuremberg trial on November 29, 1945—did not necessitate "flaps", as the poison gas was supposedly released through the shower heads inside the gas chamber.
At some point in mid to late 1945, the gas chamber promoters within or associated with the U.S. Army realised that the gassing method they had been propagating was scientifically impossible, and a decision was taken to make alterations to the building that would make it at least scientifically feasible that people could have been gassed with Zyklon B in the room (Carlo Mattogno details here, p. 225f, how numerous people came forward in 1960 claiming they had been forced by the Americans to work in the construction of a gas chamber at Dachau; the final result of which being Dr. Martin Broszat's famous letter to Die Zeit in which he stated that no one was ever gassed at Dachau, because the gas chamber was never finished/put into operation).
The American alterations to the building were completed by the summer of 1946, because the American designed "flaps" are visible in the photograph below which I brought from a photography dealer recently (it wasn't particularly expensive, and I see no reason to doubt the authenticity of the message which dates it to "summer, 1946", plus the date is corroborated by another photo from 1946 which shows the same contraption in front of the American gas "flaps"):
Unfortunately I can not read what that sign in the photograph says, even when looking at the original photograph through a magnifying glass—the text on the sign just wasn't caught in focus.
Below is the reverse of the photograph which features the following message: