Keuffel & Esser described this as a "Surveying Compass, with folding sights, graduated to degrees on raised ring, variation plate, [and] two spirit levels." The variation arc at the north end of the face extends 45 degrees either way, and reads by double vernier to 6 minutes. With polished mahogany case (here missing), this compass cost $18. K & E advertised compasses of this sort from the early 1900s through the 1940s, and donataed this example to the Smithsonian in 1972.
Ref: Keuffel & Esser, Catalogue (New York, 1906), p. 420.