Recent studies produced by historians Christian Booß and Helmut Müller-Enbergs also show domestic surveillance in East Germany went far beyond the Stasi's network of IMs. The two work at the BStU and not long ago, they happened across Stasi informant groups into which hardly any research has been conducted. They found that institutions in which people provided information about others were categorized as POZW -- which stood for "Partner in Political-Operative Cooperation." In contrast to IMs feeding information to the Stasi, these people were not forced to sign a document obliging them to pass along information. But they did so nonetheless. Numerous POZW reports are still in existence -- from banks, for example, or libraries, hospitals, registration offices and judiciary agencies.
Starting with the 1 Pf. in 1960, followed by the 10 Pf. in 1963, and the 5 Pf. in 1968, the old style coins were gradually replaced with new coins depicting the state name "Deutsche Demokratische Republik." Aluminium 1 Mark, 2 Mark and 50 Pfennig pieces were released for circulation in 1956, 1957 and 1958, respectively. In 1969, brass 20 Pfennig coins were introduced, with nickel-bronze (later cupro-nickel) 5 Mark coins issued from 1968. In 1973 and 1974, 1 and 2 Mark coins were redesigned dropping the former "Deutsche Mark" title. The brass 20 Pfennig coins were issued partly because pay telephones had a standard charge of 20 Pf. and were having problems with smaller aluminium coins jamming due to their light weight. Commemorative 5, 10, and 20 Mark coins of various types have also occasionally made it into circulation.