This striking stamp pair from Poland, issued in 1965, commemorates the "International Quiet Sun Years" (1964–1965), a scientific initiative focused on solar observation during a period of minimal sunspot activity. Designed by T. Michaluk, both stamps depict a radio telescope dish silhouetted against a vibrant sunburst, symbolizing radio astronomy's role in solar research. Though identical in theme and denomination (2.50 zł), the stamps differ in background coloration — one in bright red, the other in a more subdued brownish tone — a collectible printing variation. The vertical inscription reads: Międzynarodowe Lata Spokojnego Słońca 1964–1965.