1943, 2 zloty \"structure barbican in Cracow\", proof in olive green, single copy of the original engraving plate on gummed paper in the sheetlet format with line perforation 14 1 / 2, upper horizontal perforation double executed - by what means a probably original backdoor operation necessary was, handwritten note to the printing ink - here sample 9, very rare piece, decorative effect, expertized with certificate Ludin BPP