The thrill of the hunt lies in the fascination with collecting stamps, combined with the achievement of recognising a good specimen.

It is increasingly difficult to find fresh blood for all the grey heads that abound. However, a lot of people who started collecting as children return to the hobby when they have a bit of money in adulthood. So says Mr Kevin Drury, chairman of Stampa 2000, which ran in the RDS in Dublin last weekend. Asked to explain the motivation for collecting stamps, he says: "I suppose it's the thrill of the hunt. Trying to find something that is difficult to get. There's a certain achievement in acquiring it. There's also an achievement in having the knowledge of what stamps are all about and being able to recognise something when you see it.

"Stamps are also seen by collectors as very pretty things. They admire the work that goes into them and they have a great knowledge about how this was achieved, such as the printing methods."

The star attraction at Stampa 2000 was a one-cent magenta (the stamp's colour) from British Guyana. "It's known as the rarest stamp in the world. However, the original one-cent magenta - there was only one of them known until quite recently - is in a vault in the United States."

The one-cent magenta on exhibit at Stampa 2000 has not yet been authenticated by the Royal Philatelic Society so Stampa 2000 was unsure what to insure it for. "To be honest, without authentication, it probably doesn't have very great value. But if it turns out to be genuine, it has a huge value indeed. The other stamp, on its own without a second copy, would probably be worth about £5.6 million [€7.1 million] at this stage. This stamp, if it were genuine, probably wouldn't be worth as much as that because it would tend to devalue the other one, given that it's no longer unique," says Mr Drury.

Many people have a few stamps shoved in a drawer in the hope that they might be worth something. So how does the lay person know if a stamp is valuable? Old collections are more likely to be valuable than modern ones. "Most modern stuff will not have a huge value but the older stuff, the early Victorian material, some of that would have significant value. It can range up to several thousand pounds per stamp.

"You could go from 10 pence for a stamp that is very common to a stamp that is quite rare and would have a high value. It's purely on rarity and, to some extent, demand too. Because there are some rare stamps or rare-ish stamps that people don't seem to want from countries that are not well collected. And they don't command a high price or as high a price."

British Commonwealth stamps generally command high prices. "Anything that makes a stamp different from the norm can enhance its value, such as a printing error or flaw. People try to get something which will make their collection a little bit more interesting. It they can point to variations or varieties which are unique or rare, it makes it look more interesting to a genuine collector," he says.

And is interest in philately declining? "I would have to be honest and say I think it probably is. It is more difficult to find fresh blood who will take up from the grey heads that abound. On the other hand, a lot of people who started off as kids come back into the hobby later on when their families are well underway to being reared. They find they have a bit of money and they pick it up again."

jmarms@irish-times.ie