The usual expression of Gresham’s law, "bad money drives out good" is a mistake. Schumpeter refers to this common definition as "not quite correct." But as the statement stands, it is not just "not quite correct;" it is quite false. The opposite is true!
Standing by itself, the general statement, "good money drives out bad," is the more correct empirical proposition. Historically, it has been good, strong currencies that have driven out bad, weak currencies.
Over the span of several millennia, strong currencies have dominated and driven out weak in international competition.
The Persian daric, the Greek tetradrachma, the Macedonian stater, and the Roman denarius did not become dominant currencies of the ancient world because they were "bad" or "weak."
The florins, ducats and sequins of the Italian city-states did not become the "dollars of the Middle Ages" because they were bad coins; they were among the best coins ever made.
The pound sterling in the 19th century and the dollar in the 20th century did not become the dominant currencies of their time because they were weak.
Consistency, stability and high quality have been the attributes of great currencies that have won the competition for use as international money.
The correct expression of Gresham's Law law is: "cheap money drives out dear, _IF_ they exchange for the same price." That proposition is neither trivial nor obvious.
From Uses and Abuses of Gresham's Law in the History of Money by Robert Mundell columbia.edu/~ram15/grash.h…
