World Stamp Catalogue/Stamp Inclusion policy
In this catalogue, the term "stamp" should be interpreted as any government-issued label that are designed and issued for use in payment of postal, revenue , penalty or related charges.
Several present day postal administrations have outsource their stamp issuing activities to agencies whom design, print and distribute stamps. For examples, many countries in African regions outsource/contracting their postal to Stamperija for their postage stamps needs. This is important to consider that this is not government issued stamps and it is left up to contributor's discretion whether to include on this catalogue or not.
Other stamps were issued by governments in exile, pressure groups, political parties and organizations. These stamps are often, but not always, propaganda labels that were never actually used to pay for postal charges.
Finally, there are a subset of stamps known as "Cinderella Stamp", which are basically decorative stickers that resembles postage stamps but did not have values.