This is a masterpiece of mid-20th Century British Engineering by famous makers, Negretti & Zambra, London. To quote the trade catalogue -'This instrument provides a combined record of atmospheric pressure, temperature and humidity, by means of separate traces in different coloured inks on a single weekly chart of standard width. The three pens are spaced a short fixed distance apart on the time scale, thus allowing them to pass vertically without interference.' 
In full working condition and crucially, complete with the excellent 'birds beak' pens which are all in place, as are the three coloured ink bottles. The instrument would benefit from a good clean together with general restoration work including attention to some general surface rust marks. See extract from Negretti & Zambra's 1950 trade catalogue - note, the price at over £60 was more than double the cost of their flagship 'Regency' model. These are truly fascinating instruments and I have even seen the movements  removed, lacquered and fitted into an exhibition style presentation hardwood case.
A great opportunity for a worthwhile restoration project.