Impex Electrical Ltd.
538 High Rd., Leytonstone, London E11 (1932)
47 Victoria Street, London SW1

Impex Electrical Ltd. was not a manufacturer, but a wholesaler who sold tubes bearing the Dario brand. Additionally, Impex held the rights to the name Dario (registered Trade Mark) in Great Britain.

[2] claims that such tubes were imported from N.V. Philips in the Netherlands, but in "History of the British Radio Valve to 1940" K.R. Thrower writes: "Dario-Impex (UK): Selling Philips tubes of French production". Tubes were acquired and imported from the Frech La Radiotechnique. [3]

Dario-Impex was also used in official literature to distinguish tubes from the french La Radiotechnique, who held the Dario brand in France (Dario-RT).

There are also a few Dario radios known - most likely also imports.

Impex Electrical Ltd. obtained registration of Trade Mark in classes 8 (appartus for use in wireless telephony and telegraphy) and 13 (electrical goods) for the word "Dario" under the numbers 469519 and 469520 on the 30th of April 1926. [3]

Impex commenced an infringement action against Philip Weinbaum who tried to sell Dario tubes under circumvention of Impex. Weinbaum argued that the registration of a foreign Trade Mark for goods that the registrar does not produce himself is not valid. The court upheld the validity of the registration. [3]

[1] Monopolies Commission report on the supply of valves [...], 1948
[2] Impex Electrical Ltd vs. Weinbaum, 44 R.P.C. 405, 1927