Gros of Saint Louis

The Gros of Saint Louis stands out for its role in standardizing French currency, introducing a consistent weight of about 4.22 grams of silver that helped merchants across Europe trust it more than the jumbled coins before.

That uniformity came from Louis IX's reforms, aimed at cleaning up the mess of varying regional mints. The coin typically bore a simple cross on one side and the king's name on the other, struck at the Paris mint during his reign from 1266 to 1270. We don't know the exact mintage figures; records from that era are as scarce as hen's teeth.

Silver content varied slightly, depending on the batch, which kept things interesting for authenticators like me over the years. If you're handling one, check for the telltale edge wear from constant circulation. And yes, some specimens turn up in hoards, reminding us that not every medieval coin stayed in a king's treasury—plenty ended up in a peasant's pocket.