Instrument maker Joseph Hoskin is not listed in Charles Smart's book "The Makers of Surveying Instruments In America Since 1700" (1962), and the existence of other samples of Hoskin's work is unknown at this time.  Research revealed that Hoskin was listed in the Directories for Waltham and Watertown, Massachusetts, as working in a watch factory in 1869-71;  at Hopkins Watch Tool Co. in 1882;  and as a watch tool maker in 1884.  Edward L. Sanderson in his "Waltham Industries, A Collection of Sketches of Early Firms and Founders" lists J. Hoskin as one of the founders of the Waltham Screw Company in 1891.  

The above pictured compass is a 19th century Surveyor's compass.  It is designed such that when the compass with graduated compass ring is locked in place on a tripod, the main plate with sight vanes, bezel ring with glass, and vernier scale under the glass can be rotated 360 degrees by way of a thumb screw located on the bottom of the compass.  This Improved or Railroad Compass feature allows for angles to be measured without reference to the magnetic needle.