SULAYMANIYAH, Iraqi Kurdistan — Iran’s currency is in free-fall, falling almost 10% over the weekend, breaking through the psychologically important half-million mark to more than 600,000 rials to the dollar. The plunging currency led the Tehran bazaar to close, an event that preceded the 1979 Islamic Revolution.

Just a few dozen miles across the border, Iraqi Kurds were watching developments closely, questioning how quickly the rial rate could fall below 1 million and the consequences.