The Stasi used several other card systems to assist their postal surveillance. The Kerblochkarten (English: Kerbloch cards) system allowed storage of data encoded as a series of hand-made notches. Like other punch card systems, groups of cards could then be automatically processed by a machine based on the presence of notches and a predefined key. The Kerbloch card system made it possible to perform statistical evaluations and targeted searches on up to 350 cards/persons at a time. Importantly, this card amended the functionality of the the F16 cards and allowed the Stasi to quickly search for potential informants by querying characteristics relevant to a particular job. While anyone who has used a computer spreadsheet software today would take this sorting and searching functionality for granted, this was a highly useful tool for the Stasi, which by 1989 had amassed over 39 million index cards. (The Key to Power, 5)
- The key to power: Card indexes and other finding aids practices of State Security. Archivar 64. Jahrgang Heft 04 November 2011.
- BStU: Kerblochkarten (KK)