His credentials as a library and information scientist are based upon three of his monographs: "Syllogie aliquot Scriptorum de bene ordinanda et ornanda Bibliotheca", published in 1728; "Hochverdiente und aus bewährten Urkunden wohlbeglaubte Ehren-Rettung Johann Guttenbergs, eingebohrnen Bürgers in Mayntz" in 1741; and "Anweisung für reisende Gelerte, Bibliothecken, Münz-Cabinette, Antiquitäten-Zimmer, Bilder-Sale, Naturalien- und Kunst-Kammern, u.d.m mit Nutzen zubesehen" from 1762. The 1728 "Syllogie…" is a bibliographic examination of major history texts of the day and is in keeping with the role of historians then and now. The 1741 "Hochverdiente…" is an examination of the assertion that Johann Gutenberg was indeed the inventor of movable type – the printing press – against competing claims. Bernhard von Mallinckrodt (1591-1664) is credited with writing the first defense of Gutenberg as the inventor of the printing press in 1639 (Schmidmaier 2001), but Köhler is said to have authored second and definitive defense (Eck 2000). Köhler's third and most important work within this context is the 1792 "Anweisung für reisende Gelerte, Bibliothecken, Műnz-Cabinette, Antiquitäten-Zimmer, Bilder-Sale, Naturalien und Kunst-Kammern, u.d.m mit Nutzen zubesehen."