I agree.
As best I can tell, at his time, cities in Frisia / Friesland were self-goverend, which is why we have have Netherlands States > Leeuwarden, City of , and we have Netherlands States > Bolsward, City of.
So, Netherlands States > Franeker, City of with currency of Groot would be equivalent (those other two cities, Leeuwarden and Bolsward should probably have Groot as their currency, since the Gulden was not yet a currency in northern Low Countries in 15th century, as best I can tell).