Dipping refractometer
circa 1912
circa 1912
1950-1975
1950-1975
1910-1920
1900
1956
1918-1920
1930
1975-1982
1899-1950
1880-1910
1870-1893
1876
1998
1998
1948
circa 1923
1900-1950
1870-1940
1880-1910
1998
1998
1930-1939
1949
1898
1920-1929
1997
1870-1893
1960s
1951-1960