Signedon thermometer: F.T. Luhme & Co.
Inscribedleather case marked: Normal Alkoholometer MAGA-N
a paper label mentions "W. Gibbs."
marked on thermometer: Thermometer nach Reaumur"
stem is also marked "No. 42"; "555.1 Gram"; "Alkolometernach Tralles. Temp. 12.5° Reau: F.T. Luhme and Co."
FunctionThis is an official hydrometer for testing the proof strength of alcohol, in units of volume percentage, which was the standard of the German and American governments. The glass jar would be filled with the spirit and then the alcoholometer would be put in. The alcohol percentage would be indicated by the point reached by the liquid's surface on the hydrometer's scale.
Temperature alters the density of liquid, which would lead to inaccurate readings. In order to solve this, the hydrometer includes a thermometer, and the alcohol content readings would have to be corrected for the measured temperature using a table (except at 12.5 R, marked in red). The scale is the Réaumur scale.