I have a Swedish 1 krona coin that was passed to me in New York as a US quarter the other day.
Since it can't easily be exchanged for its current value (about 15¢) it represents a collective devaluation of the US economy by the full 25¢ value of a quarter coin.
The law prohibits me from passing the coin back into circulation, which means taking the whole 25¢ loss, myself. The alternative is to allow the devaluation to remain in effect by quietly and illegally passing the quarter along — perhaps as part of a tip, where the recipient is in the best position to launder the coin again quickly.