Catalogue
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Marconi-Osram Radio Valve Type DER, by Marconi Company, London, 1920s
Inventory Number: 80189
Date: 1920s
Maker Details: Signed by Marconi-Osram Valve Co. Ltd.
Inscription: "MOV / CO LTD" printed on underside of base. See Documents for other inscriptions.
Size: 110 mm in overall length (including base pins)
Materials: Glass, steel, brass?, plastic?, assorted metals.
Other Given Number(s): Christie's 212.
Notes:
Marconi Radio Valve (or Tube) Type DER (Dull Emitter R) with mostly silvered glass balloon envelope, steel-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, 43964).
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