Great Britain 1902 5d dull purple and blue (O.W. Official) Specimen, SGO34sGreat Britain 1902 5d dull purple and blue (O. W. Official) Specimen, SGO34s. A superb unmounted mint, with full original gum, example overprinted "SPECIMEN" type 16. A rare government official stamp used exclusively for reference purposes in the finest possible condition. The "O. W. Official" overprints were issued to Office of Works. The higher value issues from 2d and above were issued in 1902 for registration fees and overseas mail. GB Specialised