You might have heard it referred to as the "hobby of kings".
Stamp collecting is enjoyed by some of the world's wealthiest and most powerful people - this month's "$20m" sale of the famed 1c Magenta being a superb case in point.
For years it has been the preserve of those in the know; the right stamps can prove to be a superb investment, earning strong returns for their owners.
Which means the world of stamp investment can seem like an exclusive club to most of us, and one we're not invited to join.
But you don't have to be a business-minded billionaire or dedicated collector to invest in quality stamps - far from it.
Take a look at Paul Fraser Collectibles' top six stamp investments under £15,000, each chosen for their extreme rarity, high demand or great value.
1. 1840 2d Mulready envelope
 Mulready's designs were ridiculed by the British public, but they have since found popularity with collectors - Image: Wikimedia Commons |
Even the least stamp-minded individual has heard of the Penny Black, the world's first adhesive stamp - issued in Britain in 1840.
But did you know there was a whole range of postal stationary issued alongside?
The Mulready envelopes are named after the creator of their stunning artwork, William Mulready of the Royal Academy. However, the British public thought the designs were too elaborate and they were met with widespread ridicule, forcing the post office to cancel the issue just months after it hit the shelves.
Today, there are only around 38 used examples of the 2d Mulready cover known to exist. They range in price from £500 to over £500,000, but you'll be able to pick up a decent example for less than £15,000.
As an example of the world's first prepaid postage system, they'll always be in strong demand from collectors of postal history, meaning values will continue to rise as supplies start dwindling. Buy the best you can afford to stand the best chance of making a profit.
See our superb Mulready 2d cover for sale, which hails from the award-winning Mayflower Collection.
2. 1979 CIA Invert
 The stamp's central image is printed upside down on just 100 examples, which were sold to a CIA employee - Image: Wikimedia Commons |
Error stamps (those with mistakes made while printing) are some of the most sought after rarities on the market - even more so when their creation is as mysterious as the CIA invert. Everybody loves a stamp with a good story to tell and this stamp certainly fits the bill.
In 1979, a CIA employee was sent out on an errand to buy some stamps. He bought one complete sheet of 100 $1 stamps from the post office but, as he left, noticed that the rush light design was printed upside down.
Aware of the value of errors like this, he and a few other CIA conspirators kept just a few for themselves, before quietly selling the remainder of the sheet.
The US government later tried to reclaim the errors, but were unable to do so as they were sold to the CIA worker legally.
However, the CIA employees - always expected to be model citizens - were ordered to give their own examples back. According to legend, some did as they were told, while others refused and were promptly fired from the CIA.
Due to the stamp being a relatively modern issue, it is valued at around $15,000. Yet it is just as rare as the famous Inverted Jenny, which has been known to sell for more than a million.
Buy one of these, hold on to it, and you'll likely be well set for a comfy retirement in the coming years.
3. Early British Guiana stamps
 The 1c Magenta sale has reignited the market for British Guiana's early stamps, bringing new collectors and strong demand - Image: Wikimedia Commons |
The British Guiana 1c Magenta - once owned by the murdering millionaire collector John du Pont - looks set to become the world's most valuable stamp when it is offered by Sotheby's later this month.
But Du Pont didn't just collect one stamp from the former colony, he collected them all... well, nearly. As such, collecting British Guiana hasn't been very popular for years (there's no fun in collecting something if you can't get your hands on it!).
But now, Du Pont's whole collection has been brought to auction, triggering a wave of consignments, and the sale of the 1c Magenta will bring a flood of new interest to British Guiana stamps.
With new collectors comes strong demand and we can expect values to rise as those collectors compete for the scant number of stamps available.
4. India Scinde Dawk issue
 India's new collectors are keen to repatriate their nation's history - Image: Wikimedia Commons |
India has one of the fastest growing economies in the world and investors are often keen to capitalise on the ever-increasing wealth of the nation's burgeoning middle classes.
The same logic can be applied to stamp collecting, if you know what to buy.
In the world of philately, the first issue of a country is often its most valuable, prized for its ties to the nation's postal history. In India, this issue is known as the "Scinde Dawk" and is highly collectible, yet remains undervalued… for now.
A half anna stamp from the Scinde Dawk issue sold for £10,000 ($15,199) at auction in 2013. With less than 100 in existence, it is among the rarest stamps ever issued in India.
India has shown a strong interest in collecting in recent years, with many collectibles seeing top prices at auction as collectors seek to return objects of historical importance back to their home country.
It is only a matter of time before attention turns to the Scinde Dawk issue and its significance to India's postal past.
5. Russia Zemstvo stamps
 There's big money in Russia, and it's being spent on collectibles - Image: Raritan Stamps |
We all know there's big money to be found in Russia and it looks as though the oligarchs have turned their attention to collecting.
We've seen huge prices for Russian art and items relating to the country's history of late, with many top auction houses now holding sales dedicated to Russian items. This newfound popularity has also been seen in stamp collecting, with Russian postage now topping many sales.
One of the most fascinating areas of Russian postal history is the Zemstvo issue, a series of unusual stamps issued in the nation's hinterlands. Unofficially produced, there are over 3,000 varieties, with one selling for an impressive $60,000 and making a 26% on its estimate at auction in 2013.
As the market for Russian stamps continues to grow along with the country's economy, that price could be looking meagre in years to come.
6. GB Postal Union Congress complete set
 The second commemorative issue in Britain, the PUC set represents some of the most beautiful stamps ever created in the country - Image: Wikimedia Commons |
Based on figures from the respected GB250 stamp index, which tracks the price performance of the top 250 British stamps, this one is a winner for future gains.
The Postal Union Congress (PUC) complete set was the second commemorative issue in Britain, hitting the shelves in 1929. Regarded as some of the best-looking British stamps, they represent the pinnacle of philately in the home of stamp collecting.
What's more, a first day cover featuring all values from the set has seen
