Directory of American Toolmakers Information
Willis Thrall succeeded Solomon A. Jones & Co., adding "& Son" to the company name in 1960.
Possibly "S A JONES & CO HARTFORD CON"
There is little to be found in the way of surviving information on this particular manufacturer.
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.
/PDFsforInventory/WebVaIRmachinists_PDF.pdf -- contains a listing of a trisquare possibly manufactured by S.A. Jones & Co.