Antique Lufkin Micrometer Caliper No. 1843.   It has a 2" to 3" range and measures in Ten-Thousands (high precision), has a lock nut and ratchet stop.  This was a top of the line tool for it's time and used by machinists and tool makers.  The precision and smooth workings of the dials on this caliper are excellent condition.  The overall condition is good for an 80+ year old tool.  Please see photos for further assessment of condition.