Today, I discovered that the Heinrich Heine Universitäts- und Landesbibliothek in Düsseldorf provides a growing body of currently 8.000+ digitised items, including metadata (METS XML), and adhering to the URN scheme of the Deutsche Nationabibliothek for public use.

For instance, I had searched for a rare report on the German emperor Wilhelm II’s journey to Jerusalem in 1898, previously available as a scan from google books[1]:

Mühlmann, Felix. Das Deutsche Kaiserpaar im Heiligen Lande im Herbst 1898. Berlin: E. S. Mittler & Sohn, 1899.

Unfortunately, as is the case with google, they do only provide the scanned pages, but no OCR or transcribed full-text. The corpus also includes some 24 newspapers and journals, predominantly concerned with either the Rhine area or–for whatever reason–fashion, as well as 1.600+ maps.