Specifcation No. AN-C-74-A. By J. B. Carroll Co. Chicago. The Dalton dead reckoning computer was designed by Dalton and Weems and adopted by the US Army Air Corps in 1940. One side has a plastic disc style slide rule for computing speed, time and distance problems, and on the other side a rotating compass rose with a transparent disc mounted above a segment of a 360' plotting circle. This arrangement makes it possible to get a large scale for the area used by the navogator for any particular problem. Excellent condition with leather case and instruction booklet. Stock code M22290.