Between 1847 and 1948 some stamps were overprinted with "SPECIMEN" or "CANCELLED". Between 1847 and 1873 examples of new stamps overprinted "SPECIMEN" were distributed to postmasters. From 1879 the overprinted stamps were sent to the UPU for distribution to member administrations. After 1892 the overprints are restricted to values of one shilling and above until 1948. The specimen stamps are listed in Stanley Gibbons Concise catalogue.