The German Patent Office (German: Kaiserliches Patentamt) started developing a classification system for its patent documents in 1877.
[1] It was greatly expanded during the following decades and was published in seven editions between 1906 and 1958, first as "Verzeichnis der deutschen Patentklassen" and later as "Gruppeneinteilung der Patentklassen".
The DPK was also used in Sweden, Norway, and other countries in Scandinavia and central and eastern Europe.
In the 1970s, development and active use of the system publications was discontinued as most of these countries switched to the International Patent Classification (IPC).
These new IPC-based parts mainly used the IPC group numbering, but kept the original DPK subclass symbols.