Nordic Cup Open is a WDF darts tournament that has been held since 1981. It is played the day after the Nordic invitational so it is normally dominated by the Scandinavian countries, but it is an "Open", so all WDF member can participate - it is a WDF Category 3 event.
From 1981 till 1996 it was played every year. From 1996 and till today it is only played every second year
References
Nordic Cup Open Wikipedia(Text) CC BY-SA