This inventory of June 24, 1943 was written up at the time Krematorium III was completed for the Auschwitz-Birkenau camp.
At the top left, we see the building being inventoried, "Krematorium III," also known as "KGL 30a." Below that, the first room listed ("Raum 1") has been written in as "Leichenkeller 1," which literally means "morgue 1." This is the homicidal gassing chamber.
At the far right, we see that there are the categories of "Brausen" (showers, showerheads) and the written-in inventory item "Gasdichtetur" (gas-tight door). We see that Leichenkeller 1 has 14 showerheads and a gas-tight door.
The handwriting is hard to read; here is a closeup of the most important parts which is a little more legible:
This document is reproduced in Pressac, Jean Claude, Auschwitz: Technique and Operation of the Gas Chambers, The Beate Klarsfeld Foundation, New York, 1989, p. 432. Its source is given as Auschwitz State Museum Archive reference BW 30/43, p. 24.
As Pressac points out (p. 429), there are no water pipes to the showerheads, nor is 14 anywhere near enough showers for such a large room. Therefore, these items were:
...DUMMY SHOWERS, made of wood or other materials and painted, as stated by several former members of the Sonderkommando.
This inventory is absolute and irrefutable proof of the existence of a gas chamber fitted with dummy showers in Krematorium III.
These dummy showers were not placed there by chance, or for purposes of decoration, but with a very precise purpose: to mislead the people entering Leichenkeller 1/gas chamber 1, a misrepresentation implying the deliberate intention to cause them to die by inhaling a deadly gas.
This document is cited in the essay How Reliable are the Hoess Memoirs?