But in 1987 the British government extended its territorial waters to 12 miles (19 kilometers) from the coast.
Sealand's Web site states: "The official language of Sealand is English and the Sealand Dollar has a fixed exchange rate of one U.S. dollar. Passports and stamps have been in circulation since 1969 and the latter decade of the 20th century saw an impressive expansion in its activity both socially and industrially as it began to develop a growing economic base which underscored its long-standing membership of the international community of States."
But the U.K. government says it doesn't recognize Sealand, and neither do other nations. German and U.S. court rulings have both rejected its claims to independence.
Other current micro-nations include the Gay and Lesbian Kingdom on islands in Australia's Coral Sea—formed by a group of gay-rights activists in Queensland—and the Hutt River Province Principality, established in 1970 by farmers in the state of Western Australia in protest of changes to government agricultural policy.
But, as with Sealand, you won't find their names on the map.
David Miller is a senior map editor with the National Geographic Society in Washington, D.C. He says the smallest state to appear in the current National Geographic Atlas of the World is Vatican City. Located inside Rome, Italy, the Catholic city-state covers 0.2 square mile (0.4 square kilometer). (National Geographic News is part of the National Geographic Society.)
Miller said a state must meet three requirements if it is to make it into the atlas. First, it has to have land. "Secondly, it has to control territory. And third, it has to have international recognition."
Things aren't always clear-cut, Miller said. There are gray areas where "sovereignty is disputed or yet to be resolved," such as Somaliland in northern Somalia.
"Somaliland has been a state since 1991, when the country fell into chaos with fighting among warlords" and Somalia's government all but dissolved, he said.
Somaliland isn't generally recognized as a state, partly because its borders remain blurry in places due to the Somaliland authorities' inability to secure the frontier from neighboring warlords in Somalia.
No Claim Whatsoever?
But Sealand has no claim to statehood "whatsoever," Miller said.
"It's a platform. They don't have land," he said. "They might claim the platform but the land underneath, or control of the land, is just not there. And of course there's no international recognition."
Miller also points out that, since 1987, Roughs Tower has been within U.K. territorial waters.
"It is by all intents and purposes under the sovereignty of the United Kingdom. There just hasn't been a specific court challenge in the U.K. that tests ownership of the platform."
So far the U.K. government has yet to assert its authority over the Sealand. That could explain why potential buyers don't seem put off by Sealand's tenuous status.
Sealand, in keeping with its pirate-broadcasting tradition, is being marketed as a "digital paradise," attracting interest from Web companies that might prefer to operate outside established copyright laws.
Sealand's latest suitors include The Pirate Bay, which allows Web users to download pirated movies and music.
The site has launched an appeal to its customers to raise funds toward the purchase of Sealand—and has, at least temporarily, renamed its site Pirates of Sealand.
But British legal experts say that, since the platform stands in U.K. waters, U.K. laws should apply.
Prince Michael of Sealand, though, also has a more traditional sales pitch.
"The neighbors are very quiet," he told BBC Radio. "There is a good sea view."
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