Nazi concentration camp badges, made primarily of colored inverted triangles, were used in the concentration camps in the Nazi-occupied countries to identify the reason the prisoners had been placed there. The triangles were made of fabric and were sewn on jackets and shirts of the prisoners. These mandatory badges had specific meanings indicated by their color and shape. The system of badges varied between the camps.
A practice was established to tattoo the inmate identifiction numbers. This was originated in the following way: In Auschwitz, the camp numbers were initially sewn on the clothes. With the increased death rate it became difficult to identify corpses, since clothes were removed from corpses. Therefore the medical personnel started to write the numbers on the corpses' chests with indelible ink. Difficulties increased in 1941 when Soviet POWs came in masses, and the first several thousand of tattoos was applied to them. This was done with a special stamp with the numbers to be tattooed composed of needles. The tattoo was applied to the upper left part of the breast. In March 1942, the same method was used in Birkenau.
Metal stamps turned out to be impractical, and later tattooing was done with a single needle on the left forearm.
The tattoo was the prisoner's camp number, sometimes augmented with a special symbol: some Jews with a triangle, Roma with letter "Z" (from German Zigeuner for "Gypsy"). In May 1944 the Jews received letters "A" or "B" to indicate particular series of numbers.