V24 and Q amplifying valves, c 1920s.

Early commercial two-valve radio receiver, 1920-1921.

Driver's brake valve with feed valve. Secti

Sterling two-valve audio amplifier, c 1925.

Sterling two-valve audio amplifier, c 1925.

Loewe multiple valve radio receiver, late 1920s.

Manufacturing radio and television valves, c 1930s.

Woman examining Mullard valves, Radiolympia, Olympia, London, 1934.

Inhalation apparatus

Sterling audio amplifier valve, c 1925, and printed circuit board, c 1950.

Marconiphone crystal-valve radio receiver, 1923.

Brisez's bi-valve intra-uterine speculum, French, 1841-1900.