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United States stamps produced from rotary presses areperforated by machines guided by the electric eye. Themarkings vary as experiments were made in putting theelectric-eye mechanism into practice. The earliest mark-ings were a series of heavy short vertical dashes dividingthe sheet into right and left panes. Later markings arehorizontal dashes placed at the other margin of thecontinous sheet of paper on which the stamps are printed. Still other markings which are applied to the marginsof the steel plate and which, of course, print on thesheet margins of the finished stamps, are the registrationmarks to guide the printer when producing two-coloredstamps. Each plate for each color is provided with aregistration mark so that the printer will know whenhe has his paper in proper alignment. |
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