8 Reales - Philip IV

Aire-sur-la-Lys, a fortified town in Artois, was besieged by French forces under Louis XIII in the summer of 1641 as part of the prolonged Franco-Spanish conflict over the Spanish Netherlands. The town's garrison, holding in the name of Philip IV, required emergency coinage to pay troops when regular supply lines failed — a practice documented across multiple Spanish-held towns during this phase of the Thirty Years' War. These siege issues were struck under duress, often from melted plate or ecclesiastical silver, with minimal equipment.

KM#27 is among the rarer documented siege coinages of the Spanish Netherlands. Aire capitulated to French forces in July 1641.