These .stl files can be used for printing by any 3D printing method, but filament extrusion was used originally, to allow a wide range of materials to be used. To increase the recognisability of the
Source: Busch, Wilhelm: Sämtliche Briefe. Kommentierte Ausgabe in zwei Bänden, Band I: Briefe 1841 bis 1892, Band II: Briefe 1893 bis 1908, hg. v. Friedrich Bohne, Hannover:...
