USSR. SC N Bl. 2 Ка**. Block without text.

Block of USSR, 1st Union Congress of Architects. Four stamps in block 40 kopecks purple, collotype printing on thick white paper, without watermark, with gum, imperforated. Block size is 134-92 mm. Red mark of guarantee on gummed side. Price in SC catalog - 1 500 000,00 roubles. In this quality, only a few blocks currently known. Very rare, "JAM" of Soviet philately. Certificate of Kirzhner.