6th Definitive Series - Sheet Numbers

What is a plate number block or plate block?
Plate number blocks, or plate blocks, are four (2 x 2 rows) or more unsevered postage stamps with marginal paper bearing the specific number of the plate used to print the stamps.

What are plate numbers?
Plate numbers are impressions to record detals or the exact number of a printing plate. Certain early issues of Great Britain included plate numbers within the stamp designs. In many modern issues the plate numbers are on the marginal paper.

What are matched plate number blocks?
Matched plate numberblocks are four or more plate blocks of stamps with plate numbers in all positions as they appeared on the original complete panes or sheets.

What are phantom plate numbers?
Phantom plate numbers are faint duplications of plate numbers, but they are not necessarily caused by faulty plates.