Centenary of the Universal Postal Union (Bolivia 1975)

Souvenir Sheet Centenary of the Universal Postal Union it reflects the thematic directions:

An anniversary is the date on which an event took place or an institution was founded in a previous year, and may also refer to the commemoration or celebration of that event. For example, the first event is the initial occurrence or, if planned, the inaugural of the event. One year later would be the first anniversary of that event. The word was first used for Catholic feasts to commemorate saints. Most countries celebrate national anniversaries, typically called national days. These could be the date of independence of the nation or the adoption of a new constitution or form of government. The important dates in a sitting monarch's reign may also be commemorated, an event often referred to as a "Jubilee".

An organization or organisation (Commonwealth English; see spelling differences), is an entity—such as a company, or corporation or an institution (formal organization), or an association—comprising one or more people and having a particular purpose.