A German naval salinity tester complete in original fitted box. These were used to test the water on U-Boats as well as other naval vessels. This example made by Dr. Hermann Rohrheck Nachf Berlin comes complete with hygrometer, a test tube (possibly replacement) and a can containing original litmus papers. An added bonus are the original operating instructions dated 1936 with numerous hand written amendments and alterations. Box measurement 15" (38 cm).