donkey sight noun an imprecise but easily manoeuvred manual sight on a tank’s main gun US,1990
Hazelip’s method used the cupola-mounted .50 as a “donkey sight,” adjusting it to be parallel with the 90mm. — Ralph Zumbro, Tank Sergeant, p. 43, 1986
— Gregory Clark, WordsoftheVietnamWar, p. 150, 1990