A NEGRETTI & ZAMBRA TEST BAROMETER, c.1950, London, with aluminum cased mercury tube divided to 1000ft with adjustable scales and side-mounted thermometer, bedplate with bubble level, on threaded feet, cast iron cistern and rubber connecting tube, the maker's plate signed 'Negretti & Zambra, London' with model number '9705', 109cm high This barometer was for precision testing the calibration of aneroid barometers. They were supplied to the Air Ministry at an original cost of £54.