The Eternal Coin is a Long Finance thought experiment that speculates on whether a coin that never loses value could exist and, if such a coin could exist, how might it be constructed.
Michael Mainelli writes that "the more that money is a medium to exchange value across more space and more time, the more uncertainty it must contain. At the extreme, an Eternal Coin, a coin that will always be accepted at never lose its value, must simultaneously connect us with all the risks of geography and time, and all the uncertainties society holds about the future". 
Gary Wright replies, "Maybe the search for the eternal coin is what we have all been involved with and a Utopian objective that will never be realised but must be tried." 
Malcolm Cooper has written a "history" of the eternal coin, which he presented to a seminar at Gresham College.
Richard Veryard has written a brief review of Malcolm's history from a systems thinking perspective. 
"In Search Of The Eternal Coin: A Long Finance View Of History" Roundtable inspired by Malcolm Cooper's research paper of the same name, held at Gresham College on 25 March 02010.
Michael Mainelli, "The Eternal Coin – Made From Real Money: Risks In Fiat Currencies", Journal of Risk Finance, Volume 11, Number 1, pages 111-116, Emerald Group Publishing (January 02010).
Richard Veryard, "The Sempiternal Coin April 02010.