United Nations Postal Administration
Only the United Nations is permitted to issue postage stamps, even though it is an organization and not a country or a territory. In 1951, an agreement was reached with the United States postal authorities whereby the United Nations was permitted to issue stamps denominated in United States dollars for use exclusively at United Nations Headquarters in New York. Similar agreements were reached with the Swiss authorities in 1968 and with the Austrian authorities in 1979. Today the United Nations Postal Administration (UNPA) is the only postal authority that issues stamps in three different currencies: U.S. dollars, Swiss francs and euros. The stamps may be used for postage when used on mail sent from the United Nations offices in New York, Geneva or Vienna.
The United Nations issues both definitive and commemorative stamps. Usually six new commemorative issues are simultaneously released each year in New York, Geneva and Vienna and remain on sale for 12 months. At the end of that period, any unsold commemorative stamps are destroyed, and those stamps that are sold out are never reprinted. Definitive stamps, however, have an indefinite sale period and can be reprinted in the denominations required for general postal needs.
The stamps are designed to illustrate the aims and achievements of the United Nations and its family of organizations. Thus, the themes depicted on United Nations stamps are unusual in that they cover a range of global issues and problems. That, together with the bank-note quality of the printing and security procedures, makes United Nations stamps extremely popular among philatelists worldwide.