The Probert Encyclopaedia of Warfare

SNIPERSCOPE

Originally a sniperscope was a rifle sight incorporating a periscope (known during the Great War as a periscope rifle), which allowed the weapon to be aimed by a soldier under cover. Now the sniperscope has changed to a telescopic rifle sight incorporating an image intensifier so that it can be aimed in the dark.
Research Sniperscope