The Stasi surveilled the post of the GDR for nearly 40 years, starting with the founding in 1950, until the fall of 1989 when the Berlin wall fell. The number of workers in Department M rose from a few dozen in the beginning, to nearly 2,200 by the end. The largest office occupied two buildings in the massive Stasi headquarters complex in Berlin-Lichtenburg and included almost 500 employees, with the remaining 1,700 spread across 15 district administration offices. (Polzin, 105)
While the ratio of women to men in Department M shrank over the years possibly due to the increasing focus on technology and automation, it was consistently at least twice that of the entire MfS. In the beginning 80% of Department M employees were women, compared with 25% in the MfS, while in the 1960s 40% were women compared to 14%. In 1989 only 20% of Department M employees were women. (Labrenz-Weiß, 5)
Employees were subject to numerous specialized training to prepare them for their work. This included courses on typography, x-ray certification, and photography for those performing inspections. Employees who were integrated with Deutsche Post received information like electronic training for working with telegraph devices, operating postal vehicles, and other knowledge related to the movement of mail and parcels. Those employees charged with the development of specialized equipment for Department M studied engineering, paper technology, air and refrigeration systems, and the mechanics around the movement of postal and newspaper materials. (Labrenz-Weiß, 6)
While Department M employees were physically embedded in Deutsche Post locations, their activities there were considerably constrained in order to ensure the secrecy of their work. For example, they were required to sit in closed groups in the cafeterias in order to avoid direct contact with actual postal workers. Official contacts were only allowed with Stasi officers already embedded in the post control system special operations.