1 Ducat - Jacob Kettler Mitau

Jacob Kettler ruled Courland as a vassal duke under Polish-Lithuanian suzerainty, yet built one of the most commercially aggressive states in the Baltic — operating his own merchant fleet, colonizing Tobago in the Caribbean and a trading post at the mouth of the Gambia River in West Africa simultaneously. These ducats were struck at Mitau during the peak of his commercial expansion, when Courland's shipyards at Windau were launching vessels that competed directly with Dutch merchantmen.

The colony on Tobago was formally ceded to Courland by the Duke of Courland's treaty with the English in 1664, making Jacob the only Baltic ruler ever to hold Caribbean territory. These gold pieces circulated in the same decades that Courlandian ships were crossing the Atlantic.