Surveyor's Vernier Compass
"Mahn & Co. St. Louis, Mo."
length 15.5 inches; needle 5.125 inches
This compass dates from the period 1891-1906, when Herman Mahn was in business in St. Louis, trading as Mahn & Co. It has a variation arc on the south arm that extends 24 degrees either way; the vernier is moved by a tangent screw on the south arm, and reads to 2 minutes. There is an outkeeper on the south arm, and there are two level vials on the north arm. It belonged to the University of Missouri at Columbia.