"It's the only one known (in) yellow. It should have been green," Danish auctioneer Thomas Hoiland told CBSNews.com's Lloyd de Vries. "A lot of famous people have owned the stamp."
It's on its way to the Nordia 2001 stamp show in Tucson, via Registered Mail to Phoenix, where Hoiland will pick it up Monday.
Every year, collectors in Denmark, Sweden, Norway, Finland and Iceland hold a regional stamp show somewhere in Scandinavia, except when an International show is being held in the region.
This year, there's an International in Denmark in October, so the American collectors of Scandinavian stamps pitched holding the regional show in the U.S. instead, and the offer was accepted.
"There was hot competition when it was sold last time. People collecting stamps like to have rare things, like to have special things. I think maybe it's because it's been known for so many years, it's special."
It's not for sale.
"It's only here to be shown; we promised U.S. Customs," he told CBSNews.com. "We were allowed to take it in here free of charge."
And, besides, the anonymous owner he represents doesn't want to sell it. "He's a keen collector and has enough money."
The three-skilling stamp, known as the Treskilling Yellow, was issued in 1855, and used in 1857 to mail a letter.
"It was found by a little schoolboy, seven years old, who was looking through his grandfather's papers in 1883," said Hoiland "Unfortunately, he took the stamp off the letter -- you must never do that! Then he sold the stamp for seven kronor the year after, and then it has been sold many, many times."
Young G.W. Backman didn't get much for the stamp.
"Seven kronor is only one dollar, so it was very cheap," he said. "When I sold it last time, three years ago, the price was $2.3 million American dollars -- and the owner was happy for it."
Hoiland doesn't know what happened to the boy, or how he felt about the subsequent sales. "The stamp dealer who bought it sold it for, I think, $500 a week later."
Although the stamp is taken out of its vault and exhibited once a year, Hoiland doesn't think the stamp has ever been mailed before, other than when it franked the letter in 1857.
"I was asked if it was so great to mail it, and we were talking to the insurance and they said, okay if it's secure and people are taking care of it. I think the Postal Inspectors will nearly take it with them to Arizona."
In fact, postal inspectors and postal police were in evidence around the ceremony and press conference in New York Friday.
"We don't lose registered mail," declared David Solomon, U.S. Postal Service vice president for the New York metro area. "We don't lose any mail. We may misplce it, but we don't lose it."
Hoiland said he's mailing the stamp from New York to Arizona because he and an associate are staying in New York for a couple of days, "and for enjoying ourselves, it's more safe to send it." The stamp spent the night in a vault at the main post office.
Hoiland had the stamp in his possession in the flight from Denmark to New York, and said he wasn't worried. "What could happen in an airplane over the Atlantic? We were followed by...four policemen in an armored car into the plane and people were looking. 'What are the police doing here in our airplane?'" he laughed. "I think they were thinking that some criminals were on their way out of Denmark."
Each person handling registered mail is required to sign for it at each point in its trip. Unlike insured mail, items may be sent by faster delivery services, such as First Class and Priority Mail, and there's no limit to amount of coverage. The Treskilling Yellow is also insured by one of the world's leading collectibles insurance agencies, Hugh Wood, Inc.
Some stamps change color because of sunlight or the use of chemicals. The Treskilling Yellow has been subjected to several scientific analyses, the most recent about a decade ago, which have judged it to be a genuine misprint.
By Lloyd A. de Vries