The purpose of this chapter is to provide an accessible and detailed narrative which will enable collectors, dealers, museum curators and auction house staff to assess and ascribe a date (or dates) to a given instrument. The narrative is chronological and describes, decade by decade, how the technical and aesthetic features of the chronometer movement, box fittings and dial all changed over the course of the century. It also emphasises the importance of recognising that these functional instruments were frequently updated and improved over their many years of service, and that this has to be borne in mind when dating, and that such updates and improvements should be considered as part of the objects valid history and not something to be removed.
