The Häfeli DH-4 was a Swiss fighter prototype in the late 1910s, build by the Eidgenoessische Konstruktionswerkstaette.
The DH-4 was a single-seat fighter based on the successful Häfeli DH-3 design.
It was made of wood with fabric covering, and carried one machine gun.
The Swiss Air Force trialled it from May 1918 to August 1918, but the DH-4 was found to possess disappointing performance and poor handling.
Data from The Complete Book of Fighters[1]General characteristics Performance Armament