Electric Eye mark

Electric Eye marks are printed rectangular blocks or lines in the margins of sheets of US stamps. There were various marking styles and mark locations used over time.

These were used to align perforating equipment and did reduce rejected panes/sheets by a huge amount. The first stamps using this were issued in 1935 and were used on (among others) the Prexie definitive series. Comparison of centering with the previous Bureau issues will show how effective the method was. The marginal markings can be found on most US issues through to the 1950s.  File:US guttersnipe.jpg|6c airmail showing a full electric eye mark due to a mistrimmed pane File:US due with electric eye mark.jpg|1c postage due with electric eye marking in the intersection of both sheet gutters 

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