20 Sols Siege of Aire

Aire-sur-la-Lys was besieged by French forces under Louis XIII in the summer of 1641, and the city's Spanish Habsburg garrison — unable to access regular supply lines — authorized emergency coinage to pay troops and maintain internal commerce. Siege money of this type was struck from whatever silver could be gathered locally, often melted plate or bullion held by the municipality, which accounts for the irregular weight tolerances seen across surviving examples.

The city fell to France in late July 1641 after roughly six weeks of siege. Most siege coinage circulated only within the walls during that window.