The object in the two photos above appears to me to be a knob to turn the water on or off in a bathroom sink. I have two knobs exactly like this in the bathroom of my house that was built in 1938. The knobs are attached to a brass fixture exactly like the one in the photo, except that my fixture does not have a swastika carved into it.
A closeup of the panel in the center of the photo above shows that it has four push buttons, but the narrator of a film about Dachau did not explain what the buttons were for.
As seen today, there are four sets of lights in the Dachau gas chamber which might have been turned on and off by these buttons. However, in the film shown at the Nuremberg IMT, which was made by the American Army on May 3, 1945, four of the light fixture boxes are called “top vents” through which the gas was put into the room.
A display in the undressing room at Dachau in May 2007, the last time that I visited Dachau, informed visitors that all the push buttons had been stolen after the camp was liberated. The area behind the west wall of the gas chamber, which is shown in the photo above, is off limits to visitors now.
The Dachau gas chamber was described in Document No. 47 of the 79th Congress, 1st Session, Senate Report (May 15, 1945) of the Committee Requested by Gen. Dwight D. Eisenhower to the Congress of the U.S. relative to Atrocities and other Conditions in Concentration Camps in Germany. This document, which is quoted below, was entered into the Nuremberg IMT trial proceedings as IMT Document L-159.
“The gas chamber was located in the center of a large room in the crematory building. It was built of concrete. Its dimensions were about 20 by 20 feet, and the ceiling was some 10 feet in height. In two opposite walls of the chamber were airtight doors through which condemned prisoners could be taken into the chamber for execution and removed after execution. The supply of gas into the chamber was controlled by means of two valves on one of the outer walls, and beneath the valves was a small glass-covered peephole through which the operator could watch the victims die. The gas was let into the chamber through pipes terminating in perforated brass fixtures set into the ceiling. The chamber was of size sufficient to execute probably a hundred men at one time.”
You can read about the Dachau gas chamber, as shown to tourists today on my website at http://www.scrapbookpages.com/DachauScrapbook/KZDachau/DachauLife01C.html