On 28th October 1950, the currency in Poland was revalued; whereby one hundred old Zlotys became worth one New Zloty. Postmasters throughout the land were authorised to apply handstamps to their existing stocks, indicating the change with the word 'Groszy' or 'Gr'.
Interestingly, the newly printed banknotes were dated 1948, whilst the newly minted coins were dated 1949!
There are over 40 different types of these handstamps known, with each Post Office having its own unique style, often with variations of the same type used at different Offices within the same town or city.
Over thirty of the existing stamp issues of Poland were authorised to receive these handstamps, including the popular 1948 'Honouring Presidents of the United States' set, a restricted issue which was printed in small sheetlets of sixteen stamps with se-tenant labels.
Such a wide combination of stamps and different handstamps have made this a fertile area for specialisation - a perfect area in which to grow a good Polish or post- war topical collection!