“During the Holocaust, concentration camp prisoners received tattoos only at one location, the Auschwitz concentration camp complex, which consisted of Auschwitz I (Main Camp), Auschwitz II (Auschwitz-Birkenau), and Auschwitz III (Monowitz and the subcamps). Incoming prisoners were assigned a camp serial number which was sewn to their prison uniforms. Only those prisoners selected for work were issued serial numbers; those prisoners sent directly to the gas chambers were not registered and received no tattoos.
“Initially, the SS authorities marked prisoners who were in the infirmary or who were to be executed with their camp serial number across the chest with indelible ink. As prisoners were executed or died in other ways, their clothing bearing the camp serial number was removed. Given the mortality rate at the camp and practice of removing clothing, there was no way to identify the bodies after the clothing was removed. Hence, the SS authorities introduced the practice of tattooing in order to identify the bodies of registered prisoners who had died.
“Originally, a special metal stamp, holding interchangeable numbers made up of needles approximately one centimeter long was used. This allowed the whole serial number to be punched at one blow onto the prisoner's left upper chest. Ink was then rubbed into the bleeding wound.
“When the metal stamp method proved impractical, a single-needle device was introduced, which pierced the outlines of the serial-number digits onto the skin. The site of the tattoo was changed to the outer side of the left forearm. However, prisoners from several transports in 1943 had their numbers tattooed on the inner side of their left upper forearms. Tattooing was generally performed during registration when each prisoner was assigned a camp serial number. Since prisoners sent directly to the gas chambers were never issued numbers, they were never tattooed.”