Silver Jubilee issue
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In philately, a Silver Jubilee issue is an issue of postage stamps by the British Post Office and the Post Offices of Commonwealth countries and British dependencies to commemorate the monarch's twenty-fifth anniversary on the throne.
In the 20th century there were only two such events, that for George V in 1935 and for Elizabeth II in 1977. These stamps, which are often rather lavish in design in comparison with definitive issue stamps, have a potential for serious appreciation in value over time.