Upon entering Auschwitz, prisoners were assigned a camp serial number which was sewn to their uniforms. This serial number was not issued to the prisoners sent directly to the gas chambers and was not registered. Prisoners who were in the infirmary or who were going to be executed were marked by the SS authorities by writing their serial number on their chest. Due to the high mortality rate and practice of removing clothing from prisoners, there was no way to identify the bodies, and the practice of tattooing the prisoner was established.
In the beginning, the tattoos were made by a special metal stamp with interchangeable numbers made up from needles allowing the whole serial number to be punched at once at the prisoner’s left upper chest. After which ink was rubbed into the bleeding wound. When the stamp method was proved to be impractical, a single-needle device was introduced and the site of the tattoo changed to the outer side of the left forearm. Although, several prisoners from different transports from 1943 had their tattoos made on the inner side of their left upper forearms. Tattooing was generally performed at the registration when the prisoners were given serial numbers.
Soviet prisoners of war who were brought to Auschwitz in October 1941 were the first prisoners to be tattooed. In the Spring of 1942, the SS started systematically tattooing all Jewish prisoners deported to Auschwitz. Tattooing was also applied to severely ill prisoners, mainly Poles, who were transported from the camp hospital at Auschwitz I to the new Birkenau camp or Auschwitz II. The practice of tattooing expanded in early 1943 due to the escape of a female Polish prisoner in February. From that point on, all incoming and already registered prisoners were tattooed on the lower left arm.
However, some categories of prisoners were exempt from the tattooing practice. This included German prisoners, ethnic German inmates, police prisoners, or non-Jewish labor-education prisoners from different nationalities. In addition to these categories, Polish civilians deported after the Warsaw Uprising in 1944 were not tattooed. Some Jewish prisoners who were held in other transit camps also avoided being tattooed.
The first series of numbers, before tattooing was introduced in 1941 and remained in use until 1945. This first series went up to 202,499. In 1941 new series was introduced and was in use until 1944. Mainly Soviet prisoners of war were given these numbers. The third series began in March 1942 with the arrival of the first female prisoners and was in use until May 1944. Around 90,000 women were identified by this serial number. The all-new series began with ‘’1’’.
In mid-May 1944, with the large number of Hungarian Jews being deported to Auschwitz, a separate series was introduced to avoid the excessively high numbers from the general series. This new series began with an ‘’A’’ following the number up until it reached 20,000 and then would change to ‘’B’’. Women series ‘’A’’ for unknown reasons did not stop at 20,000 but instead at 30,000.
Few other specialized series of numbers were introduced. A series for ‘’reeducation’’ prisoners in January 1942. These numbers were assigned retroactively to these ‘’reeducation’’ prisoners who had died or were released. Another specialized series was also introduced for Gypsy prisoners in February 1943 with the serial number starting with Z, for Zigeuner which is Gypsy in German.