A letter bearing the Penny Black stamp of 1840, which was used five days before it was legal to do so, will be on show at Stampa '98 next weekend. Opening on Friday, the three-day event is being held at the RDS. The customary price for a used Penny Black is in the region of £10-£100, while one sent on the first day of official issue - May 6th, 1840 - can sell for £10,000-£20,000. However, because of its rarity, the example on display is expected to fetch £200,000 or more when it is auctioned next year.

This is just one of the thousands of rare and unusual stamps which will be on show. The rarest Irish item on display will be a strip of four twopenny stamps issued in 1935 especially for vending machines. Only 25 unused examples of these stamps still exist and this particular strip is valued at £50,000. The only difference between this stamp and a normal twopenny stamp from the period is the lack of perforations on the left and right-hand sides of the former.

International experts are expected at the show and will be offering free valuations of stamps and postmarks. Dealers and collectors from throughout Ireland are expected to attend along with those from England, Germany, Canada and the US. Millions of pounds' worth of stamps will be available for sale, both from the dealers and from more than 40 British Commonwealth countries represented by the Crown Agents stand, as well as from the Irish and Isle of Man post offices.

An Post will sponsor a special children's area with a wild animal theme to tie in with the recent issue of the "endangered species" range of stamps. This area will have stamp-related games and entertainment as well as "goody bags" for young visitors. Furthermore, a limited edition miniature sheet of the endangered species stamps will be on offer to the first 2,000 visitors to the show; these are likely to become collectors' items.