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WW1 RANGE FINDER TYPE FT 27, 1917
Range Finder No2 Mk3
Looking through the eyepieces on the left is a scale in feet, and on the right two images of the scene, when both images are in line, by adjusting a knob on the tube, the range can be read in the left eyepiece.
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- This is an 80cm base coincident image range finder. There were two forms, one for the army and one for the navy. These differed only in the manner in which the two images were presented to the observer. The images to be brought into alignment were always shown one above the other in the view. The Army type had the upper image inverted as a mirror image of the lower, but the naval type had both images identical. I believe the scale is in yards, not feet. Though it could be used when held only by the folding handles shown, there was also a chest & shoulder brace which helped prevent movement and made reading easier, and a tripod to increase stability even further. There was also an astigmatizer switch; this device was intended for use on a single point of light such as a star; its image being stretched into a vertical line so that the required alignment of the two images was easier for the operator.
.......... Tony Williams, Goldcoast, Australia, 21st of September 2011