Danish Patent and Trademark Office
Jørgen Burghardt tells us the Danish Patent and Trademark Office and its data go back to 1864. There was a reform in 1894 which seems not to have made a big difference.
Burghardt analyzed foreign filers in a sample of Danish patents.
The current Danish Patent and Trademark Office has a web site at http://www.dkpto.org/ Danish Patent and Trademark Office.
- Danish patent classifications -- The same or very similar to the German one. Notably, klasse 77 refers to aeronautics.
The Danish patent office used the German Patent Classification (DPK) for many years. Gruppeneinteilung der Patentklassen (Grouping of the patent classes) started in 1877 in Germany and had seven editions between 1906 and 1958, and with a total new edition in 1975 based on groups from IPC. The DPK has 89 classes, most with subclasses and subgroups. The Danish patent administration published a printed version in Danish in 1938.