The idea by Salvador Dali is amazing: 22K-gold coins -- legal tender in his kingdom; smart & funny --, minted by the Le Locle-based goldsmith Huguenin S.A. in 1966 and used in watches and jewellery by Piaget ("House of Gold") in the 1970s.

And it would have been a full monetary & economic success if combined with coercive power & taxation-claims. :-)