Abstract: An assembly for attachment to a rotatable shaft of a machine tool, for example, a lathe, for indicating translational movement of a member selectively in one of two scales, including two dials graduated one in each said scale, an idler pinion connecting the two dials, the number of teeth on each dial engaging the idler pinion giving the required conversion ratio, and an indexable sleeve surrounding both dials and being movable to reveal only a selected scale at any one time.