Yes it can be from a Firefly.The swedish antiaircraft forces had the Firefly as a targettowing aircraft using a private Company ( Svensk Flygtjänst ) in the fifties.They later bought a couple of Gloster Meteors as a successor.The training aera was located 50-60 km from the finnish Island Alandia across the Baltic sea. I shall check if there was a Firefly accident in the area.