Topic: PPR (the Polish Worker's Party)

The following Polish postage issues commemorate meetings and anniversaries of the Polish Worker's Party:

Fischer 583-585 - 10th PPR anniversary in 1922
Fischer 1144-1148 - 20th PPR anniversary in 1962
Fischer 1995 - 30th PPR anniversary in 1972
Fischer 2644 - 40th PPR anniversary in 1982
Fischer 3726 - underground mail during martial law, commemorated in 2000