Due to many Varieties and Flaws: Deegam, Modern British Philatelic Circle (MBPC), Machine Collectors Club (MCC) and Stoneham (STN) also contributed. To summarise their contributions:
Ribbed Gum (Connoisseur Catalogue.
Phosphor Bands varieties e.g. Short bands. Inset Bands (Deegam Catalogue).
Reference Numbers for Booklets and Panes (MBPC, MCC Catalogue, Deegam & Stoneham Catalogues ).
Perforation Types for panes and margins (MBPC, MCC Catalogue, Deegam & Stoneham Catalogues).
Screened Values (Connoisseur Catalogue).
In addition to above, during printing of stamps, phosphor bands shifted to the right or left.
Our online shop have all the images of the Errors, Flaws and Varieties.