Think twice before you discard old envelopes, particularly if they were posted in far flung places or bear unusual post marks.

Whyte's of Dublin regularly holds stamps and postal history sales, with many items fetching handsome prices. Letters from 1800 and 1850 were recently sold to a collector for £800, almost double the guide price, while a rare handstruck "Charity Letter" stamp sold for £850. Old envelopes can fetch anything from £30 to £1,000. The most valuable among the most recent lot were stamps, envelopes and banknotes with unusual markings, such as "UK banknotes overprinted with Saorstat Eireann 1922" and a Boer War two-shilling stamp overprinted "Mafeking Besieged".