5 Cents

John Sidney Clunies Ross ruled the Cocos (Keeling) Islands as a personal fiefdom, and the token coinage he issued was the only currency accepted on the islands — workers on the copra plantation were paid in these tokens, redeemable only at the company store he controlled. The arrangement was feudal in every practical sense. Australia formally annexed the islands in 1955, but the Ross family retained control until 1978, when the remaining islanders voted to integrate with Australia and the token system finally collapsed.

Plastic ivory was chosen over metal specifically because it could not be spent anywhere else on earth — a deliberate design to prevent capital from leaving the island economy.