Czechoslovakia built a prototype derived from a BH-21 in 1926, what is its models hallmarks?
Avia BH-23: The Avia BH-23 was a prototype night fighter aircraft built in Czechoslovakia in 1926. Avia BH-23:  The design was derived from the BH-21 day fighter, incorporating structural changes made to the BH-22 trainer, and the type was originally designated BH-22N. Fighter aircraft:  The hallmarks of a fighter are its speed, maneuverability, and small size relative to other combat aircraft.
The hallmarks of a fighter are its speed, maneuverability, and small size