Great Britain 1840 1d Black Plate 4, SG2.
A very fine used close to large four margin example lettered OB, neatly cancelled by the distinctive violet Maltese Cross. Violet cancellations were from Market Street, Hertfordshire, Glasgow and Manchester only.
A magnificent exhibition quality example of this lovely coloured cancellation, very rarely seen in so fine a condition.
Accompanied with a 1996 British Philatelic Association certificate of authenticity.
The Stanley Gibbons specialised catalogue value (last published in December 2011) is £12,000.