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Marconi Radio Valve Type DER, by Marconi Company, London, c. 1925

Inventory Number: 15591

15591-2t 15591-1t

Date: c. 1925

Maker Details: Attributed to Marconi-Osram Valves.

Inscription: "MARCONI / VALVE / PATENTED / MADE IN ENGLAND" printed on exterior surface of bulb. "BBC [LOGO] / D.E.R. / FIL. 1.8 VOLTS / 1462A" printed on exterior surface of bulb.

Size: 110 mm in overall length (including base pins)

Materials: Glass, bakelite, steel, assorted metals.

Other Given Number(s): Christie's 212.


Marconi Radio Valve (or Tube) Type DER (Dull Emitter R) with partially silvered glass balloon envelope, polished black bakelite base and four steel base pins. The construction was of a cylindrical anode with a helical grid passing through it, threaded by a filament. BBC logo ("ENTIRELY BRITISH MANUFACTURE") was used between September 1924 and 1927 and is a good indication of date of origin. Previously catalogued with two other, similar Type DER Radio Valves (Inv. Num.s 43964, 80189).

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