The new office houses a computer containing information on stamps for sale-about one million at the moment. Traders can gain access to the exchange, and make trades, through their own personal computers. Or they can trade through brokers at the exchange or through any of 150 dealers who are exchange members.

Sellers set the “ask” prices they want for stamps, which they turn over to be graded and insured by exchange officials and stored in vaults pending their sale. Meanwhile, buyer’s submit “bid” prices, which are compared with the sellers’ ask prices. If the bid and ask prices match, a computer automatically records a sale. If the prices are close, the buyer and seller are invited to negotiate. When sales occur, the exchange typically collects a commission of 3% from buyers and 6% from sellers. That compares with a commission of 10% collected from each side at most major stamp auctions.

One advantage for the collector is access to up-to-date prices. Previously, if an investor sought to sell stamps, say, six months after a catalog was issued, the printed price would often be outdated. And unscrupulous dealers could take advantage of the difference. The exchange also enables investors to quickly shop around for the best price. At the same time, individual dealers can offer a wider range of stamps to clients without personally having to store them.

Rousso, the exchange’s chairman, says his computer network will “inject fresh money into the market that will benefit everybody.” In its first six months, the exchange handled about $1 million in transactions, Mr. Rousso says.

Dealers say that’s still only a tiny fraction of philatelic revenue, which many estimate at $500 million a year. Yet some participating collectors are enthusiastic. The exchange “has done for stamps what Nasdaq did for the OTC market in the 1970’s, “ says Moshe Rimson, and avid collector and the president of M. Rimson & Co., a New York stockbroker. Adds Lewis Berg, the vice president of Southeastern Stamp Co., a Hollywood, Fla. Auctioneer: “It should bring the stamp business into the modern era.”