This instrument belonged to the University of Missouri-Columbia. It dates from the late
19th century, but represents a form that was widely used in the 18th century. It has a pair of sight
vanes (one missing) attached to the circle, and another pair on the alidade. The circle is
graduated to 30 minutes, and read by vernier to single minutes. Henry Blattner and Frank Adam
were brothers-in-law, in business together from 1872 to 1891.