One of the faithful readers of this blog sent me a copy of the catalog of the Marbach exhibition on Zettelkästen for which I am very grateful. It is entitled Zettelkästen, Maschinen der Phantasie and edited by Heike Gfereis and Ellen Strittmayr. Johannes F. K. Schmidt reports on Luhmann's Zettelkasten (pp. 84-92). It's an informative article. Among other things, it makes clear something that I knew already—at least sort of—namely that Luhmann's Zettelkasten contains actually two strata (one from about 1951-1962) when Luhmann was a public servant, the other from about 1963-1996 when Luhmann was more interested in sociology. In the illustrated part, under "k" for "Kommunikationspartner," there are four pages of pictures. In the Introduction we find out that Luhmann was a very frugal person and therefore used bills and other documents which contained text on just on side to write his notes. Since these documents were usually DIN-A4 and his Zettelkasten used DIN-A6, he could easily cut the originals in half. In another publication I read that he even used the pictures his children had made in school for this purpose. Accordingly, the quality of the paper is uneven and often inferior. His mythological machine does not look like much. Nor does it easily give up its intellectual secrets to the uninitiated observer.
Still, his Zettelkasten was (and is) a great inspiration for me, even though his theory leaves me rather cold.