Abstract: A support is provided defining abutment surface portions from which one end portion of a dop stick may be supported in position paralleling and at least substantially coinciding with a predetermined axis against lateral displacement in any direction and for axial shifting relative to the support, as desired. The support defines four mounting locations spaced about the predetermined axis and disposed in a plane normal to the axis and spaced along the latter from the abutment surface portions. Elongated micrometer spindle, sleeve and thimble assemblies are supported from the mounting locations and extend along radii of the predetermined axis and the micrometer sleeve portions are supported from the corresponding mounting locations for adjustable axial shifting relative thereto. The free ends of the micrometer spindles may be spaced equally from the aforementioned axis in order to support a gem stone in centered position relative to the axis for mounting on the supported dop stick.