The instrument itself is a baro-thermograph, a specialized version of a barograph that records both atmospheric pressure (on the main chart) and temperature (shown by the integrated thermometer). It was manufactured by the French firm Richard Frères. This specific model features an 8-capsule aneroid bellow and a centigrade thermometer, a design very popular for naval and professional use during the late 19th and early 20th centuries. This model is dated circa 1882 - 1891. The instrument is very clean, in great condition and comes complete with original key and small weight. The instrument winds smoothly and the winding mechanism appears to be in full working order. The thermometer also works well.