High frequency (violet ray) apparatus, England, before 1966
before 1966
before 1966
1920-1940
1925-1950
1950-1960
1920-1940
1925-1935
1920
1925-1940
1890-1950
1880-1910
1903-1904
1903-1904
1903-1904
1920
1920-1950
before 1966
1903-1904
1903-1904
1903-1904