The catalog uses an own numbering system, but with kind permission from Stanley Gibbons, the main numbers from the Great Britain Concise Stamp Catalog are included.
Shades and varieties of main numbers have a subnumber a, b, c, etc. For example, 1a, 1b, 1c are shades of number 1. Plates and dies of main numbers have the plate or die number separated by a dot. For example, 1.1a, 1.1b, 1.2 are plates of number 1.
Plates and dies do have SG numbers but are hidden in the listings except at the stamp details where it is visible.
This catalog follows the same order as in the book with the exception of SG numbers 121 (2s. brown) and 151 (1s. orange brown). This means that some Stanley Gibbons numbers are found elsewhere in this catalog. For example, the die I and II of the first perforated issue are grouped and mixed in the Stanley Gibbons catalog, but are separated in the book, where first die I is discussed and then die II.
The visibility of subnumbers in the regular stamp list, have list and want list, can be changed by an option on the main menu; initially subnumbers are visible. Likewise, the visibility of plates and dies can be changed; initially plates and dies are visible.
The book does not list every shade (or names the shade differently) that is listed in the Stanley Gibbons catalog; in that case, a masculine ordinal indicator ° is used to indicate this. Issues later than 1917 are not included in the book but are added to complete the King George V period.
Only main numbers have images, sub numbers, plates and dies have not. At the stamp details, gray scale images of main numbers are used for the sub numbers. In the regular stamp list, images of sub numbers are not displayed. In the have and want list, the colour images of main numbers are used for the sub numbers.
Other catalog numbers from the major worldwide catalog publishers can be added manually. The codes used for the catalogs are: 'SG' for Stanley Gibbons, 'Sc' for Scott, 'Mi' for Michel and 'Yv' for Yvert & Tellier.
You can manually add a price, but the catalog does not distinct between the condition of stamps like used, mint, hinged, etc. With kind permission from Arthur Ryan & Co., the catalog can import stamp prices of various grades as published in July 2014 on the web site www.gbstamps.co.uk.
The Find by Design option gives an overview with all stamps. Scrolling for the first time in this overview might be slow because of the many images that must be loaded! Scrolling a next time will be faster. For fast scrolling, it is tried to load all images into memory and it depends on the available memory on the device if this is possible. If this is not possible, a message is shown and scrolling in this overview will be slower than usual.