10c red and 15c red SEEBECK 'Postage Due' issue, a fine mint IMPERF inter-panneau block of four consisting of two of each value, without watermark, from the original printing on thin paper with horizontal mesh and clear gum. The block has a complete 'Hamilton Bank Note Eng & Ptg Co. New York' imprint at bottom. The plate lay out of eight panes of twenty five allowed for the gutter pairs of different values. (D154B & D155B variety)