Each work book was given an individual number, the so-called work book number (Arbeitsbuchnummer). The work book numbers of civilian forced laborers were preceded with the letter A from 1943 onwards. The first digits indicate the employment office that issued the work book. If there are letters after the dash, a sub-office of the employment office was responsible for issuing the work book. The work book number ends with consecutive numbering specific to the issuing office. Zachary Kisleczok, for example, was the 752nd civilian forced laborer for whom the Rosenheim employment office issued a work book for foreigners. Work book numbers can also be found on other documents relating to an individual, such as on many company personnel cards.