Poland 1960 – 100 Years of Polish Postage Stamp, Block of Four × 60 gr, Used

Commemorative block of four 60 gr stamps issued in 1960 to celebrate the centenary of the Polish postage stamp (100 lat polskiego znaczka pocztowego). Violet/purple background with a stamp-within-a-stamp motif featuring the Warsaw Mermaid (Syrena Warszawska) design in blue. All four stamps cancelled (CTO or postal). Fischer Bl.21 / Michel Bl.22. Block in protective sleeve/holder. Light bends visible at corners on reverse; overall good collectible condition.