Catalogue
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Marconi-Osram Radio Valve Type DER, by Marconi Company, London, c. 1923
Inventory Number: 43964
Date: c. 1923
Maker Details: Signed by Marconi-Osram Valve Co. Ltd.
Inscription: "MARCONI OSRAM VALVE / MADE AT THE OSRAM LAMP WORKS / COVERED BY VARIOUS PATENTS" printed on exterior surface of bulb. See Documents for other inscriptions.
Size: 120 mm in overall length (including base pins)
Materials: Glass, nickel, plastic?, brass?, assorted metals.
Other Given Number(s): Christie's 212.
Notes:
Marconi Dull Emitter Radio Valve (or Tube) Type DER (Dull Emitter R) with mostly silvered glass balloon envelope, nickel-plated plastic? base and four brass? base pins. The construction was of a cylindrical anode with a helical grid passing through it, threaded by a filament. Previously catalogued with two other, similar Type DER Radio Valves (Inv. Num.s 15591, 80189).
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