Valve-gear on Boulton & Watt rotative engine, 1788.

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

'How to build a two valve set', No 17, Godfrey Philips cigarette card, 1925.

Mitral and aortic replacement heart valves, 1970s.

Woman with Marconi transmitting valve, Radiolympia, London, 1936.

'How to build a two valve set', No 8, Godfrey Philips cigarette card, 1925.

Two Starr-Edwards artificial cardiac valves, 1978-1979.

Two Starr-Edwards artificial cardiac valves, 1978-1979.

Demonstrating the latest x-ray equipment, 7 December 1938.

Fleming diode, British, 1905.

Fleming diode, British, 1905.

Vauxhall 'E type 30/98' motor car, 1919-1922.