Notes: "The K&E model 4071T is the familiar Cox Duplex with the addition of a single trig scale to each side, and an L scale. This particular 4071T can be dated with unusual precision thanks to K&E’s numerous small changes over the life of this model. The clamshell cursor makes it pre-1915, the L-shaped, adjustable end brackets make it post-1911, and the location of the “L” scale on the edge vs. the face makes it pre-1913. "
