1 Ryō 'Suruga Sumikaki Koban'

The Suruga Sumikaki Koban belongs to the earliest phase of Toyotomi Hideyoshi's attempts to impose monetary order on a fragmented Japan. Struck in Suruga Province, the "sumikaki" designation refers to the ink-brushed inscriptions applied by mint officials — a quality-control authentication practice that predates the standardized stamp systems Hideyoshi would later enforce. These provincial koban predate the Tenshō Ōban centralization effort and reflect a transitional moment when regional gold production was being pulled under the control of a nascent national authority without yet being fully absorbed by it.