The complete set in detail

SS20B
Sc Nr. O20
1927 - Official stamp : Orange-red overprint (33 degree angle) 'Dienstmarke' - 30 Cts. ; green

SS21B
Sc Nr. O21
1927 - Official stamp : Orange-red overprint (33 degree angle) 'Dienstmarke' - 40 Cts. ; sepia

SS22B
Sc Nr. O22
1927 - Official stamp : Ultramarine overprint (33 degree angle) 'Dienstmarke' - 50 Cts. ; carmine-red

SS24B
Sc Nr. O24
1927 - Official stamp : Yellow-red overprint (33 degree angle) 'Dienstmarke' - 75 Cts. ; dark brown

SS25B
Sc Nr. O25
1927 - Official stamp : Yellow-red overprint (33 degree angle) 'Dienstmarke' - 1Fr. ; violet

SS26B
Sc Nr. O26
1927 - Official stamp : Blue overprint (33 degree angle) 'Dienstmarke' - 2 Fr. ; red-brown