10 Dollars - Princess Joan I Jubilee

Sealand — the former Royal Navy Maunsell sea fort HM Fort Roughs, seized by Paddy Roy Bates in 1967 — declared itself a sovereign principality and began issuing coins in the 1970s largely as a revenue exercise. The "Princess Joan I Jubilee" issue commemorates Bates's wife Joan, whose claim to the title rested entirely on her husband's self-declared sovereignty over a rusting platform seven miles off the Suffolk coast. The X# prefix in the reference confirms its status as a non-circulating fantasy piece, cataloged by Krause under their Unusual World Coins classification rather than as recognized currency.