Herbert 4 Senior Capstan (and Monoslide Lathe) with Dial-Change Headstock -identifiable by a 4-spoke, capstan-style wheel on the face of the headstock : Parts Manual as Exploded Component Drawings.
Herbert 5 Senior Preoptive Capstan and 5 Senior Preoptive Monoslide lathes. Spare Parts Manual as clear and detailed Exploded Component Drawings (this is the last edition with fuller details).