The currency of the Empire consists of gold, silver, and possibly copper coins of varying values. While the most commonly used coins are the gold Suwani and sinku, as well as the silver Denari and the Soruda, as coins of either silver or copper are commonly used as pay in the Imperial Army. In addition to these common coins, there is a wide variety of less valuable coins, typically of silver, which may be minted by various localities.
Much like the coins of the real-world Roman Empire, while the coins are presumably hand-struck, they are intended to have their weight as uniform as possible in an era prior to mass production, and are valued based on their actual weight in precious metals. For instance, the most valuable gold coin, the Suwani, about 60 grams, and is worth five times the amount of the smaller gold sinku.
Since the dead at the Battle of Alnus Hill were buried with all possessions, including coins, there has been a shortage of currency in the Empire. After JSDF's sets a shop and trading hubs at Alnus Hill, it is unknown whether the citizen of the Empire is using the Yen or paper money or not.
The coins of the Empire are similar in appearance to the currency of the Roman empire. The denari coin is even based off the real-world Roman denarius.