Gresham's Law needs some reconciling. I get what it's saying, but we also have the phenomenon of harder money displacing easier money over time, like the move from seashells or salt to precious metals.
Discussion
I've been thinking about the reconciliation. Gresham's law and the phenomenon of moving towards harder money are consistent with each other.
Bad money driving out the good = value transferring out from those saving in bad money to those saving in good money.
Naturally, the velocity of the bad money is going to be high: people are trying to get rid of it as quickly as they can. This velocity increases until it gets to a critical points and the bad money is discarded, suddenly and entirely.