This is  a hardwood cased barograph is in very good condition and one of the last produced by F. Darton and Co of Watford. The company had along history, formed in 1834 and traded until 1992 when the business was taken over by fellow instrument makers, Russell Scientific.
This barograph is basically in traditional format with a two-compartment chart drawer, however, there is a slightly different arrangement in the way the linkage transfers the pressure movement from the diaphragm stack to the pen arm which also incorporates the pen lift-off feature. Quite an ingenious invention and works extremely well alongside more standard designs. There are two makers' plaques - one to right of the baseplate and the other inside the chart drawer.
The instrument comes with its original instruction leaflet as well as a reprinted copy of an instruction pamphlet by Negretti and Zambra with guidance on how to interpret chart readings. I have also shown the extract from Darton's trade catalogue,, prbably the last. 
It uses  standard weekly recording charts – a selection will be included together with a fresh bottle of recording ink. 
317mm wide x 190mm high x 175mm deep.