Gresham's law

グレシャムの法則 ／ greshams-law　—　Phenomena

The rule of thumb known as: bad money drives out good.

Monneron of 2 sols1791

⚠ There is a condition for this to hold true: the law must stipulate that both circulate at "the same face value." If the recipient is allowed to inspect the content and change the price, good money will not be driven out.

In other words, this is not a law of metals, but a law of institutions.