Danzig Physicians & Natural Scientists MiNr. 306 MiNr. 307 MiNr. 308 Danzig issued this set on 29 April 1939 to commemorate German physicians and natural scientists. The stamps depict: 10 Pf — Johann Gregor Mendel 15 Pf — Robert Koch 25 Pf — Wilhelm Röntgen Set Date(s) 29 April 1939 Watermark(s) None Album Page(s) Physicians & Natural Scientists MiNr. 306 MiNr. 307 MiNr. 308 Danzig issued this set on 29 April 1939 to commemorate German physicians and natural scientists. The stamps depict: 10 Pf — Johann Gregor Mendel 15 Pf — Robert Koch 25 Pf — Wilhelm Röntgen Set Date(s) 29 April 1939 Watermark(s) None Album Page(s)