This is a travelling or desktop barometer in a folding case by Negretti & Zambra, London, circa 1939. The case is finished in a red Morocco type finish which closes flat and opens to reveal the pocket size barometer. all in good condition although one of the hinges to the case has become disengaged. The set hand is operated by turning the outer ring either left or right. These instruments were popular presentation gifts in the 1920s and 1930s. 
Attached is an extract from the Army & Navy Stores sales catalogue of 1931 describing a similar instrument with various options for finishes.
105mm x 105mm x 20mm