This type pocket stereoscope was produced for the British Army in WW2. These Viewers were used to look at Stereo Photos taken from Reconnaissance Aircraft during the War. The viewer is assembled by locating the steel arms which are spring loaded into the slots and these arms have grooves to enable different length adjustment for viewing the Photos. The viewer measures 15cms x 6cms max size of frame and 8.5cms long. It is in excellent condition.