A 3.25 inch (8.26 cm) deep by 4.5 inch (11.43 cm)wide by 13 inch (33.02 cm) high grey wooden box with a 45 degree mirror at either end with a 3 inch (7.62 cm) by 4 inch (10.16 cm) viewing slot on each end.
Early trench periscopes were made by installing two mirrors at 45-degree angles at either end of a long box or tube. During the winter of 1914–1915, soldiers on the front lines used these improvised box periscopes, also known as hyposcopes. Most measured between 30 centimetres and 100 centimetres in length.
In early 1915, commercial manufacture of box-type trench periscopes began in the United Kingdom. However, demand exceeded supply until 1916. To make up for the shortfall in commercial supply, British Army workshops behind the front lines started to manufacture trench periscopes in mid-1916.
Advertisement for the Trench Periscope
WATSON’S is the TRENCH PERISCOPE supplied by Watson’s to the British Army.
It enables the user to see over obstructions 18 inches higher than his eyes.
By its means, the soldier can see what is happening above and beyond the Trenches without exposing his head. The Reflectors give an undistorted view -a vitally important feature. Perfectly simple. No complications. Metal Casing.
THE ORIGINAL AND THE BEST IS WATSON’S’ GIRAFFE
Price 8/6 Wooden box & postage in Great Britain, 1/- extra. To France, 2 MANUFACTURED EXCLUSIVELY BY W. WATSON & SONS, Ltd., Opticians to H.M. Government, $13, HIGH HOLBORN, LONDON, W.C.
Send for Watson’s List of Naval & Military Instruments,
Secondary Card Describes periscope No. 9. Mark II with 22.5 inches between mirrors) TRENCHSCOPE CO 1917.
When observing with a binocular, rest it on the glass screen. When observing without a binocular, lower the shutter until the eyes are protected by it and the glass screen.