Looking at the Sweden catalough there are two duchies minting their own coins for a short period.
Could they be made their own duchies as seperate issuere, under Sweden?
Or other suggestions on what to do?
Charles as Duke of Södermanland is the same as the later King Charles IX of Sweden.
John, Duke of Östergötland is not a later king of Sweden. Not only titular duke, but ruling duke.
Södermanland, Duchy of
House of Vasa:
Charles (IX) (1560 - 1611)
Östergötland, Duchy of
House of Vasa:
John (1606 - 1618)
Sources:
https://en.wikipedia.org/wiki/S%C3%B6dermanland#Dukes_and_Duchesses_of_S%C3%B6dermanland
https://en.wikipedia.org/wiki/Charles_IX_of_Sweden
https://en.wikipedia.org/wiki/John,_Duke_of_%C3%96sterg%C3%B6tland