The WADP Numbering System (WNS) is a project referencing postal stamps issued in the world since 1 January 2002.
It is monitored by the World Association for the Development of Philately (WADP) and the Universal Postal Union.
Its publication appeared on a website where visitors can look for an issue by country, date, topic or key words.
Since 2002, some developing countries succeeded to reduce their philatelic program and officially denounce illegal stamps via the UPU.
[1] When declared, each isolated stamp with a graphic difference (in the design, denomination, color or dimensions) is given a WNS number :