Stamp collecting is a popular hobby that also can pay off financially. Stamps and related postal objects can be beautiful and exotic, plus they often have historical value. And as VOA's Mil Arcega reports, the stamp trade is beginning to attract serious investors.

It's the world's largest stamp show. Held only once every 10 years - the World Philatelic Exhibition opened earlier this month in Washington D.C.

The show attracts stampafficionados, dealers and postal organizations from all over the world. Some come here to buy, sell, or trade -- but most come simply to admire the variety of stamps on display, including some of the world's rarest.

Whatever the reasons, stamp dealer Bob Prager says an increasing number of collectors are now seeing stamps as commodities. "The first reason for collecting anything is for the love of the item or the stamp. But there are more people coming in, looking for ways of investing money, and hopefully getting a return on their investment. "

But investing in stamps is not a game for amateurs. "It is like any business. You have to know a lot about what you do."

And Prager says even professionals make mistakes. He admits he's lost money on some stamps but says he's also had his share of winners. He offers as an example, an inverted U.S. stamp, known as "121-B".

"My collector purchased this probably about six, seven years ago, probably for about $40,000. It is now worth about $60,000."

British-basedphilatelicfirm Stanley Gibbons, which specializes in alternative investments, says rare stamps were among the top four investments of the 20th century, with an average annual return of about 10 percent.

Prager says the secret to making money is patience -- waiting for the right stamp to come along and knowing when to sell it. That's where professionals come in.

"I don't hold a stamp very long. I buy and sell and buy and sell. So it is different. I am in and out of a stamp but I like to place it with a collector so that one day when they get tired of their stamp collecting and they want to sell their collection they will come to me to buy it from them, so I try to sell them the right things to begin with. I want to buy my own stamps back."

Stamp collecting is among the world's most popular hobbies. Philately organizations say more than 30 million stamp collectors help fuel the estimated $10 billion a year industry.