Poland 1960 Centenary of Polish Stamps 1.55zl Block of 4 Used CTO

Block of 4 stamps commemorating 100 years of Polish postage stamps (“100 lat polskiego znaczka pocztowego”). Denomination 1.55 zloty. Green background showing a red stamp-within-stamp design (1945 dove/eagle stamp). All four stamps bear a circular CTO cancellation “Chelm Lubelski 27.VI.45”. Corner block with full margins and top selvage inscription. Condition: Used / CTO (cancelled to order).