it is likely that many remain unrecorded. Both national and local entities have issued them. Governments have sometimes combined the functions of postage and revenue stamps. In the former British Empire, such stamps were often inscribed "Postage and Revenue" to reflect their dual function. Other countries have simply allowed revenue stamps to be used for postage or vice versa. A revenue stamp authorized subsequently for postal use is known as a postal fiscal. Bhutan, for instance, authorized the use of revenue stamps for postal purposes from 1955 until the first proper postage stamps of the country were issued in 1962. In the Stanley Gibbons catalog, this type of stamp has an F prefix. Methods of cancellation While revenue stamps often resemble postage stamps, they are not normally intended for use on mail and therefore do not receive a postal cancellation. Some countries such as Great Britain have issued stamps valid for both postage and revenue, but this practice is now rare. Many different methods have been used to cancel revenue stamps, including pen cancels, inked handstamps, perforating, embossing, hole punching or simply tearing. From around 1900, United States revenue stamps were required to be mutilated by cutting, after being affixed to documents, and in addition to being cancelled in ink. A class of office equipment was created to achieve this which became known as "stamp mutilators". Collecting Revenue stamps were once widely collected by philatelists and given the same status as postage stamps in stamp catalogues and at exhibitions. After World War One, however, they declined in popularity, possibly due to being excluded from catalogues as the number of postage stamps issued rose rapidly and crowded revenues out. The lowest point in revenue philately was during the middle years of the twentieth century. A Stanley Gibbons children's stamp album from the 1950s warned in its introduction: "Since Philately is the collecting of stamps that are employed in connection with the Posts, do not put in your album fiscals, telegraph stamps, tobacco-tax labels and other such strange things as are often found in some collections." This is not a definition of philately that would be recognised today. More recently, revenue philately has become popular again and now has its own FIP (Fédération Internationale de Philatélie) Commission and is an approved category in FIP endorsed stamp exhibitions. Many catalogues have been issued by specialist publishers and dealers but revenue stamps still do