This law states that “bad money will drive out good”, i.e. with two currencies in play with the same value, the one which cost more to be made will be driven out by the other. The reason for this is cited to be an increased premium for melting down the currency for its higher worth and using the cheaper version as currency instead.
Diagrams
Originated from/Coined by
Sir Thomas Gresham
Further Reading/ References
https://en.wikipedia.org/wiki/Gresham%27s_law
http://www.economicsdiscussion.net/greshams-law/greshams-law-of-the-monetary-systems-with-explanation/12714
http://www.triallawyermoney.org/what-is-greshams-law/