Plate number


A plate number is a number printed in the margin of a sheet or roll of postage stamps, or on the stamp itself, which shows the printing plate used to print the stamps.
A plate number is the serial number of a printing plate. It is printed in the selvage or border of a pane of postage stamps.
Philatelists and stamp collectors analyze or collect plate numbers and stamps with different plate numbers, often as a block, thereby known as a plate block. The American Plate Number Single Society is an example of a specialist philatelic society which focuses on single stamps with plate numbers. APNSS is affiliate #178 of the American Philatelic Society