The Japanese Type 99 Arisaka rifle was equipped with anti-aircraft sights and this is how they worked.
The Arisaka rifle was the general issue rifle of the Japanese army during WWII. It was essentially the Japanese equivalent to the U.S. Springfield or the Russian Mosin Nagant rifles.
The Arisaka rifle had a standard aperture sight for aiming. However, it also had another interesting feature for locating targets. A flip up ladder sight allowed the shooter to compensate for bullet drop for targets up to 1,500 meters away. In addition to the ladder sight, the Arisaka rifle also had two arms that flipped down to the sides of the rear sight. These arms allowed the shooter to roughly estimate for the airspeed of passing airplanes.
Check out this great video to learn more about this interesting feature of the Arisaka rifle.
It may sound far-fetched to damage a flying airplane with a bolt action rifle, but it may have actually been effective early in the war. This feature was later eliminated later in the war in order to save supplies.
I wonder if a plane or pilot was ever taken down using the somewhat primitive sights on the early Arisaka rifle?