English, c.1900, engraved to the silvered face 'Negretti & Zambra' , the weather watch pocket barometer with three concentric silvered dials, outer ring indicating pressure, ring for wind direction, center with altitude correction and windows for fall rise and steady, rear of case with letter codes for forecasts, case circumference with altitude correction scale, in velvet lined dark red Morocco case,

Footnote: responds to plastic bag test

Forecasting weather with the Negretti & Zambra Weather Watch - This pocket barometer contains Negretti & Zambras Weather Forecaster, which was patented in 1915 and developed based on real weather conditions observed over a span of ten years. To forecast the weather, you can set the wind direction and align the central disc with the steel pointer on the dial. Adjusting the altitude correction involves rotating the rear cover until the arrow lines up with the appropriate level on the scale engraved on the side of the case. By considering whether the pressure has been rising, falling, or remaining steady, along with the season (summer or winter), you can read the letter that appears within the corresponding sector in the center of the dial. A detailed description of its operation can be found on page 89 of Banfield's book "BAROMETERS Aneroid and Barographs", with an illustration on page 87.