Stamp catalogs take part of the basic equipment of the serious philatelist; classification and evaluation of the collected stamps is possible without help of the catalogs.
One has to differentiate between specialized and general catalogs. The specialized stamp catalogue is made for the collector of special interest mostly in one area, meanwhile the general catalogs are listing - in a simplified manner - the stamps of the whole world.
Preface of catalogs and introduction to each stamp section, as well as the specifications of each stamp enriches your philatelic knowledge and contributes to the protection from the acquisition of less worth or false stamps.
Specification to the printing, type of paper, perforations, gum etc., as well as the mentioned the date of issue and validity period permits a first evaluation of the stamps as well as of their cancellations.
Comparating the value of different stamps the same edition of catalogs should be always used. Only items of equal quality niveau should be comparated; inferior or exceptional quality demand price discount or surplus.
Stamp catalogs are indispensable for classification and evaluation of stamps : no trade and no exchange without specification of the catalog references. Only the stamp catalog gives a sense to the collecting activity, because the systematical structure of the collection is only possible with the catalogs' help.