Never throw out an old envelope, particularly if it has come from the other side of the world and has plenty of colourful stamps and franking on it.

Take today's sale of stamps and postal history at Whyte's of Marlborough Street. The dense catalogue lists dozens and dozens of envelopes and cards, which may sell for £30, £50 or up to £1,000, depending on their markings.

Almost 1,200 lots of postal stationery and stamps go under the hammer in the sale, which starts at 1 p.m. The most valuable lots are stamps, envelopes or banknotes with unusual markings, such as "UK banknotes overprinted with Saorstat Eireann 1922" (£900-£2,000), and a Boer War two- shilling stamp overprinted "Mafeking Besieged"(£1,600).

An 1841 UK penny red, used on a letter from Dundalk to London, and cancelled by a Maltese Cross postmark in red instead of the regulation black is considered very rare and is expected to make £600. A ship letter which travelled from Guyana to London but carries a handstruck stamp of Buncrana, Co Donegal, could make £2,500. The sale may be viewed this morning up to noon.