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. The American Plate Number Single Society (APNSS) is an example of a specialist philatelic society which focuses on plate numbers. APNSS is affiliate #178 of the American Philatelic Society
- "The American Plate Number Single Society". Retrieved December 13, 2010.