HARWICH - RARE DARK BLUE BOXED 'HARWICH/SHIP LETTER' ON COVER FROM NETHERLANDS - Oct. 1851 E from HAARLEM to London with mostly fine strike of this mark. A similar mark in a different shade of blue, then described as unique in blue, and of a similar date was sold by Cavendish in 2008 for £800+.Cross Reference: SHIP LETTERS, NETHERLANDS (Image)