29c New York Stock Exchange Bicentennial inverted block of four
The block of four shown is actually a double error block. Two of the stamps have the black printing inverted, and the other two have the black missing. Further, portions of the black printing appear in the right and top margins. These varieties occurred because of the way the press sheet was formatted. The panes were separated by gutters (areas without stamps), the vertical gutter being one stamp wide and the horizontal gutter one stamp high. In addition, there were wide margins at the right and bottom of the sheet. Each error pane consequently had twenty-eight inverts and twelve missing centers.