S. Robert Jackson
Watertown, New York
Directory of American Toolmakers Information
DAVIS & COOK/WATERTOWN N.Y.; DAVIS & COOK; MANUFAC'D BY DAVIS & COOK * WATERTOWN N.Y. (sometimes in a circle);
Hynson appears to have primarily supplied Davis & Cook levels and supplies and he notes that he has succeeded them in the catalog in our collection.
Nelson, Robert E., Ed. (1999). Directory of American Toolmakers: A listing of identified makers of tools who worked in Canada and the United States before 1900. Early American Industries Association.
S. Robert Jackson. (no date). The Level You Need. Facsimile of the original. Reprinted by Martin J. Donnelly Antique Tools.