Ebay seller pasapik (who is also ismaa3) from near Madrid in Spain sells these Principality of Sealand CD plates.
Sealand is a 30m x 30m ancient and rotting concrete tower in the North Sea just off the UK coast that some joker has claimed as his private kingdom. There are no vehicles there and there is no legal plate that has ever (or will ever) be issued by that ‘country’. This is perhaps a new category of plate – the fantasy plate (a phrase coined by a friend of mine; respect brother). It might also be called a souvenir plate.