This alidade has an inverting telescope, striding level, vertical arc reading 30 degrees each way, and separate trough compass. It is part of a complete plane-table outfit that Keuffel & Esser described "as made for the U.S. Coast and Geodetic Survey" and that sold for $175. The Survey
acquired this example in 1893
Ref: Keuffel & Esser, Catalogue (New York, 1906), p. 408.