Here we have a Vintage LUFKIN RULE CO. USA No. 166, 6" Precision Toolmakers Machinists Square. It has a precision ground steel blade and steel stock with a hardened and tempered blade. It is in Very good 'used tool' condition with an occasional light corrosion mark, scratch or stain. Overall blade length is 7-1/4" (6-1/8" to the stock).  Blade is 1-3/8" wide. Stock is 4-3/8" L.  No Owner marks. Please review the pics to confirm condition !!