The description and the analysis of Oswald Lohse's astrophotographic plates, collected at the Astrophysical Observatory Potsdam in the period 1879 -1889, are presented. 67 plates of the archive, taken with the greatest instrument of the observatory at that time -the refractor (D = 0.30m, F = 5.40m, scale = 38 /mm) and with the second heliographic objective (D = 0.13m, F = 1.36m, scale = 152 /mm) -survived two world wars in relative good condition. The plate emulsions are from different manufacturers in the beginning of astrophotography (Gädicke, Schleussner, Beernaert, etc.). The sizes of the plates are usually 9×12 cm 2 , which corresponds to fields of 1.2 • and 5 • respectively for each instrument mentioned above. The average limiting magnitude is 13.0(pg). Besides of the plates received for technical experiments (work on photographic processes, testing of new instruments and methods of observations), the scientific observations follow programs for studies of planet surfaces, bright stars, some double stars, stellar clusters and nebulous objects. Lohse's archive is included into the Wide Field Plate Database (http://www.skyarchive.org) as the oldest systematic one, covering the fields of Orion (M42/43), Pleiades, h & χ Persei, M37, M3, M11, M13, M92, M31, etc. With the PDS 2020 GM + microdensitometer of Münster University 10 archive plates were digitized.