This instrument has a wooden base with two metal reels that hold a loop of paper in place. A crossbar over the frame at the back carries a hollow circular protractor that moves over the paper. The protractor is divided to degrees. It also has an alidade with scales on both sides of it. Both the ring of the protractor and the alidade may be rotated. One side of the alidade has a scale in which six inches equals one mile, the other eight inches to one mile. On the left side of the frame are holes for six pencils, with pencils. On the right side is a part of a compass and a clinometer scale that reads from 40 to 0 to 40. The position of the compass can be fixed by turning a screw on the back of the instrument. A short belt attached to the back of the base makes it possible to wear the device on the arm. The instrument fits in a leather pouch with metal clasp and leather strap. There is additional paper in the pouch.
According to the 1904 Gurley catalog, this instrument was designed for the use of civil and military engineers and surveyors in reconnaissance and topographical surveys. In 1898, it was "given an extensive and successful trial in Cuba and the Philippines, as well as in the United States."(p. 205)