D M overprints

Fischer U15-20 | Michel Dienstmarken 15-20 | Year of issue 1922

Fischer U15
Michel 15
Fischer U16
Michel 16
Fischer U17
Michel 17
Fischer U18
Michel 18

Fischer U19
Michel 19
Fischer U20
Michel 20

Translations

D M is a German abbreviation for Dienstmarke, meaning "official stamp".
Freie Stadt Danzig is German for "Free City of Danzig".