sentences:  The new stamp was only valid locally, and mail addressed to foreign destinations continued to be franked with British stamps.The United Kingdom joined the General Postal Union (later known as the Universal Postal Union, UPU) on 1 July 1875, and since at the time the postal services in Malta were deemed to be part of the British Post Office, the islands were effectively also part of the union.Malta claims to have been the first British colony to join the UPU, although due to its status as a colony it did not gain full membership until independence almost a century later.