Surveyor's Vernier Compass
"Roach & Warner, N.Y."
length 13.875 inches; needle 5 inches
John Roach and Henry Warner were in business together in New York for a few years around 1840, trading as Roach & Warner, and advertising surveying compasses and other
instruments "of their own manufacture, warranted accurate and at lower prices than can be had at any other establishment." This compass has a variation arc on the north arm that extends 20 degrees either way; the vernier is moved by a large screw on the south arm, and reads to 2
minutes. There is a level vial on each arm.