Righi pattern oscillator, 1870-1923
1870-1923
1870-1923
1894
1964
1960
1952
1928-1929
1949-1950
unknown
1894
1870-1923
unknown
1960
unknown
1960-1979
unknown
1894
1870-1923
1962
1969
1952
circa 1950
circa 1950
1952
circa 1950
1937
circa 1950