Lathe Trav-a-dial
Imperial travadial originally off a lathe but you can fit these to any machine tool that requires precise measurement of an axis, infinite travel, extremely accurate and much nicer to read compared to a DRO especially when roughing. Missing the mount hence the cheap price but can adapt to fit however you want. Yes I can post. http://www.lathes.co.uk/trav-a-dial/