1 Solidus - Friedrich and Wilhelm Kettler Mitau, type 2

Friedrich and Wilhelm Kettler ruled Courland jointly following the death of their father Gotthard in 1587, though the arrangement was perpetually fractious — Wilhelm's increasingly autocratic conduct eventually led the local nobility to expel him in 1616, after which Friedrich governed alone. Billon solidii of this joint issue circulated across a duchy that remained a Polish-Lithuanian vassal state throughout this period, obliged to maintain coinage consistent with the 1580 monetary ordinance of the Commonwealth.