According to the 1880 U. S. Census, Samuel Phelps of Grafton, Vermont was born 1815 in Vermont.  Both his parents are listed as having been born in Vermont as well.  Phelps is listed as a Surveyor and Farmer.

The pictured unfinished compass was purchased by a collector in Vermont and sent to Pennsylvania to be finished.  There is no actual evidence that Samuel Phelps was an instrument maker; therefore, the maker of the unfinished instrument is technically unknown.