Photograph of four individuals gathered around an 11-foot coincidence rangefinder at Fort Casey. The individual second from left is operating the range finder while the rest observe. A coincidence rangefinder or coincidence telemeter is a type of rangefinder that uses the principle of triangulation and an optical device to allow an operator to determine the distance to a visible object.
The range finding pit was infilled below the mortars at the beginning of World War II (1939/1940). Photo c. early 1940s but printed 22 August 1970 at The Little Gallery in Oak Harbor.
