Since 1967, the facility has been occupied by the former British Major Paddy Roy Bates; his associates and family claim that it is an independent sovereign state. External commentators generally classify Sealand as a micronation rather than an unrecognised state. While it has been described as the world's smallest nation, Sealand is not currently officially recognised as a sovereign state by any sovereign state. Although Roy Bates claims it is de facto recognised by Germany as they have sent a diplomat to the micronation, and by the United Kingdom after an English court ruled it did not have jurisdiction over Sealand, neither action constitutes de jure recognition as far as the respective countries are concerned.
Technically speaking, Sealand has a point when they claim independency, altough it's a country without real territory. Sealand has issued passports and has operated as a flag of convenience state, and it also holds the Guinness World Record for "the smallest area to lay claim to nation status".
Sealand is not a member of the Universal Postal Union, therefore its inward address is a PO Box in the United Kingdom and Sealand's stamps should be considered as cinderellas.
The website: http://www.sealandgov.org/
Stamps of Sealand: http://www.sealandgov.org/shop.html#Stamps