Franking - Wikipedia
Franking comprises all devices, markings, or combinations thereof ("franks") applied to mails of any class which qualifies them to be postally serviced. Types of franks include uncanceled and precanceled postage stamps (both adhesive and printed on postal stationery), impressions applied via postage meter (via so-called "postage evidencing systems"), official use "Penalty" franks, Business Reply Mail (BRM), and other permit Imprints (Indicia), manuscript and facsimile "franking privilege" signatures, "soldier's mail" markings, and any other forms authorized by the 192 postal administrations that are members of the Universal Postal Union.[1]
While all affixed postage stamps and other markings applied to mail to qualify it for postal service is franking, not all types and methods are used to frank all types or classes of mails. Each of the world's national and other postal administrations establishes and regulates the specific methods and standards of franking as they apply to domestic operations within their own postal systems.[2] Although there are differences in the manner that the postal systems of the 192 nations[3] that belong to the Universal Postal Union (UPU) apply and regulate the way their mails are franked, most mail types fall under one (and sometimes more) of four major types and/or methods of franking: postage (stamps, etc.), privilege, official business, and business reply mail.
Any and all conflicts that might arise affecting the franking of mail types serviced by multiple administrations which result from differences in these various postal regulations and/or practices are mediated by the UPU, a specialized agency of the United Nations which sets the rules and technical standards for international mail exchanges.[4][5] The UPU co-ordinates the application of the regulations of postal systems of its member nations, including as they relate to franking, to permit the servicing and exchange of international mail.[6] Prior to the establishment of the UPU in 1874, international mails sometimes bore mixed franking (the application of franking of more than one country) before the world's postal services universally agreed to deliver international mails bearing only the franking of the country of origin.
