Croatian National Bank API
Live official exchange-rate data from the Croatian National Bank (Hrvatska narodna banka, HNB), the central bank of Croatia, against the euro — uniquely with three rates per currency (buying, selling and middle): the official rate for every published currency, a single currency's buying/selling/middle rate plus the inverse, a currency's official rate on a specific past date, and currency conversion between any two published currencies (including the euro) cross-computed through the euro at HNB middle rates.
api.oanor.com/hnb-api