In December 1948, the communist Polish Workers Party was united with the Polish Socialist Party to form the Polish United Workers Party.
Date inscription XII.1948
PPR is the Polish Workers Party (Polska Partia Robotnica).
PPS is the Polish Socialist Party (Polska Partia Socjalistyczna).
PZPR is the Polish United Workers Party (Polska Zjednoczona Partia Robotnicza).
Kongres jedności klasy robotycznej = The congress of the unification of the working classes.
These stamps were first issued in different colours and with the date inscription "8.XII.1948" instead of "XII.1948" as Fischer 479-481.
Polish United Workers' Party
Polish Workers' Party
Polish Socialist Party
People's Republic of Poland
Fischer 484 (part of a sheetlet)