SOURCE: BBC (4-30-09)
It is among 27 Penny Blacks, first issued in the UK in 1840, and found on letters impaled on spikes in the loft.
It has a catalogue value of £15,000 but its condition means auctioneers in Denbighshire value it at £5-6,000.
The letters were encrusted with bird droppings which may have helped preserve the stamp collection of 400.
The stamps, including Penny Reds, were found in the property in north Wales, with many valued at £200 each.
Colin Knights, owner of Aqueduct Auctions in Froncysyllte in Denbighshire, said they were found by chance as the building was being cleared.
Among the find were 27 Penny Black stamps and 400 Penny Reds and Penny Red-Browns issued between 1841 and 1848.
The most valuable Penny Black is from a rare issue, plate 11.