A simple trip to a British post office turned into a life-changing adventure for one lucky stamp collector.

In 1967, a stamp enthusiast went to his local post office in the north England town of Rochdale to buy a pair of Great Britain stamps. He paid one shilling and nine pence (less than 10 US cents) for a pair that celebrated the invention of the television and featured a silhouette of Queen Elizabeth II.

What he didn’t realise until later was that one of the stamps was missing the queen’s head. It was a lucky purchase. In 2014, he sold the stamp, known as SG 755b, at auction for £23,600 ($36,260).

Although the advent of email has hurt postal mail service in recent years, stamp collecting remains a passionate hobby as well as a valuable business and investment strategy in many countries. Billions of stamps have been issued since the British Penny Black, the world’s first adhesive stamp, debuted in 1840, and many are laced with romance and lore — transporting collectors to exotic destinations, critical moments in history and, for some, elusive future fortunes.

In 2014, the one-cent magenta — an unassuming magenta octagon with handwritten black script released in British Guiana in 1856 — set the record for the most money ever paid for a postage stamp. The sum was $9.5m, nearly a billion times its original penny value.

Though numerous collectors have deep pockets and decades of knowledge, anyone can become a rare stamp aficionado.

And even if you aren't as lucky as the Rochdale collector, you can quickly become knowledgeable about a range of topics and geographic locations as you build a stamp collection. Knowing what and how to buy is key.

“You learn a lot about the world in an effortless but pleasant way,” said retired dealer Anthony Grainger. “Collecting should be a pleasure and if you eventually make money, that’s a bonus.”

Getting started

Any philatelist (the official name for stamp researchers and collectors) will tell you this: build your collection around a focus that interests you, whether it’s cars or birds or your family’s country of origin. This way stamps become a vehicle for learning about a broader subject in all its nuances, said Dominic Savastano, a stamp specialist at Spink London. “With knowledge you can beat the dealers,” he said.

Like most stamp experts, Savastano started collecting as a young boy in England and quickly grew intrigued by the process of finding and sorting miniature works of art from places near and far.

“You have a pile of stamps, and you start arranging them by country,” Savastano said. “Some of course are turned upside down and you realise this one has grilled gum [patterns in the adhesive] on the back from Czechoslovakia! Stamp collecting is very much an aesthetic hobby. You buy stamps because you want to enjoy looking at them.”

What you’ll pay

You get what you pay for when it comes to rare stamps. While there’s no firm rule on pricing, collectors buying at auctions should expect to pay 40% to 50% of the catalogue price, said Joseph Cottriall, who works as a stamp valuer for Warwick & Warwick in the UK, and a consultant to Sotheby’s in the US. The catalogue price is the amount listed in industry-respected publications by the likes of Stanley Gibbons in London, Scott in the US, Michel for the German-speaking world and Yvert et Tellier in France.

When deciding how much you’re willing to spend, first determine how rare the stamp is. Some of the world’s most coveted examples are the result of printing errors (like the British television stamp without the queen’s head), but others may have become scarce due to political or historic circumstances. Sometimes, the piece of mail a stamp is fastened to — perhaps a letter displaying traces of war history — can raise the price by a few hundred dollars.

The most prized stamp Cottriall has ever encountered is the inverted Jenny, an American stamp from 1918 depicting a blue old-fashioned biplane surrounded by a red vintage border. It looks like your average classic stamp until you realise the plane, or Jenny, was printed upside down. One hundred examples slipped through the printers, each worth at least $100,000 today, depending on condition.

“I looked at it under a magnifying glass and was like, ‘Wow, this is the value of a house!’” Cottriall recalled.

Quality is paramount. Generally, a mint stamp (one straight from the post office) will cost more than a used stamp. Mint stamps should be in mint condition, meaning no tears, folds or colour damage as well as an intact “stamp hinge” (the paper coating that guards the adhesive on the back). Even a stamp worth a few dollars could fetch a couple hundred if it’s the best example of a specific design on the market.

Stamps should be kept in high-quality albums or stock books. These generally range from about $75 to $150. “Hingeless” albums are considered the safest because they contain individual plastic sleeves that don’t require sticking stamps to pages, which can damage a stamp’s back. Albums should be stored in a cool place, away from areas that can get cold and damp or hot and humid.

What to look for

Older stamps are generally more valuable than modern stamps, Savastano said. Most modern “special” and “commemorative” sets released by countries for publicity and economic reasons have little value since so many are printed.

“In England, practically anything that’s been issued in the past 45 years immediately drops to 60% of face value,” he said.

Value can also change dramatically over the course of a decade or two, depending upon politics and collector interest. Take China for example. In the 1960s, few people wanted to buy stamps from a communist country. But today, a sheet of stamps from 1962 called Stage Art of Mei Lanfang is worth around $15,000.

China, Hong Kong, Japan and India are all in high demand at the moment, reflecting the growing trend of collecting in Asia. Western European stamps, on the other hand, are dropping in value. That’s because collectors who have been buying such countries as Switzerland, Germany and Italy for the past 60 years are now selling and flooding the market. However, classic stamps from these countries can still be valuable. Stamps from the UK, Commonwealth countries and the US tend to retain value since so many people continue to collect from these nations.

Where to buy it

While finding a rare stamp at a car boot sale or an antique shop might fit the idealistic story of a lucky find, the majority of known rare stamps have already been snapped up.

You’re better off going to a reputable dealer or auctioneer who can certify a stamp’s authenticity. The dealer Stanley Gibbons is considered an international authority, and specialist auction houses include Warwick & Warwick, Spink, Corinphila and David Feldman. In theory, auction houses are cheaper since dealers add markups that can double the price. But auctions are driven by bidders, and bidding wars can inflate prices substantially higher and create a lot of variance in the final sale.

Stamp fairs such as Stampex and travelling world stamp exhibitions are great places to meet dealers and scout out stock.

While the internet has enabled collectors to pursue their hobby ever more fervently, buying online is risky. It’s tougher to discern fakes and defects, or to spot the fine details of colour and pattern that separate a common stamp from its celebrated sister. Still, many people buy on sites like eBay, and it could play to a buyer’s advantage if the seller doesn’t know bogus from big money.

“There is no substitute for experience,” Cottriall said. “Collect a country or period you are interested in; learn about the people, culture and stamps issued; and you could become an expert.”

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