Each plate is given a unique serial number which appears in the margin of the plate. A stamp may be printed from a single plate, or in the case of common stamps printed in large quantity, there may be scores of plates. Most plates include a tablet with the Bureau’s name; these occur in several different formats in the margins. Many plates include guidelines and/or arrows that indicate where the printed sheet is to be cut into panes. In many plates, the siderographer’s initials appear in the margin as well. The approval signatures or initials generally appear in the bottom margin of the CPP, but may appear anywhere on the sheet. Enlarge the 10-cent Louisiana Purchase CPP and scan down to the bottom margins to see these markings.
