Great Britain

1875 2½d rosy mauve watermark anchor (SG.138), plate 3 on blued paper, tied on cover to Constantinople with clear Birmingham duplex, the red 'British Post Office Constantinople' receiving mark (partial) on reverse. A scarce stamp in its own right (cat. £5,750 as off-cover single) and a rarity on cover. Accompanied by 1988 RPS certificate.