Sound toll + End sound toll modifiers.
It says "known country" ? it should be DAN anyway, but the Sound toll is awarded to whoever controls:
owns = 6 # Skåne
owns = 12 # Sjaelland
owns = 14 # Fyn
This mission is own given if the owner of Sjaelland has Sound toll, although if someone had it, but has lost it sinc eyou got the mission that might bug the relations option out, you could still go for the military one though.