second congress of the General Postal Union was held in
The congress decided to change the name of the organization to Universal Postal Union. This was mainly due to the influx of new members, especially the British, French and Dutch colonies, making the membership universal.
There were other changes to the treaty. The original treaty allowed "overseas" countries to be admitted to the union subject to the agreement of administrations having postal relations with them. The 1878 congress decreed, however, that any country could accede directly to the union merely by unilateral declaration and communication of that declaration to the Swiss government.
Also the 1878 congress decided to introduce postal money orders, the 'T' to be put on unstamped letters, the Registration label with the letter 'R' and the 'Valeur declarée' (declared value).
In 1978 a number of countries issued postage stamps to
commemorate the congress in
Stamp catalogue - centenary