The Deutsche Lehrer-Bücherei (german teachers library) is the predecessor of the Bibliothek für Bildungsgeschichtliche Forschung (library for the research on the history of education) in Berlin. Established in 1876 as Deutsches Schulmuseum (german museum on schools), renamed as teachers library in 1908, renamed again as Pädagogisches Zentrum (peadogic centre) in 1945, and turned into the institution it is now in 1992, the old teachers library did two things. It was an institution for the vocational training of teachers and a centre for research on schools and pedagogy. [The stamp above was used by the Cassianeum Donauwörth (Bavaria), a catholic secondary school in the mainland of german catholism, which is only fitting, as the journal is the "catholic journal on teaching and education".]
The old stamp, used here, combines an oval form, used in quite a lot of libraries at the time, with a more rustical pattern, citing “classical antique” forms.
During its existence as teachers library, the institution used different stamps. Seen here, on the cover of a journal on teaching materials, are two different stamps. The one above resembles the one before, but the pattern used around the oval border is different.
The other stamp, used here on a journal for upper secondary school without latin, leaves place for the numerus currens used for shelving. (It still is used in the library today, although with a different system, counting the years in front of the actual number.)
As you can see by further inspection, the number itself is stamped also – it’s a stamp in a stamp.