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Mullard Radio Valve Type PM4, by Mullard, England, 1930s

Inventory Number: 21856

21856-2t 21856-1t

Date: 1930s

Maker Details: Signed by Mullard.

Inscription: "REGISTERED / TRADE MARK / MULLARD / RADIO VALVES / PROTECTED BY PATENTS / 1128" printed on exterior surface of bulb. "MULLARD / PM4 / [TRADEMARK] / REGISTERED TRADE MARK" printed on exterior surface of bulb.

Size: 95 mm in overall height (including base pins)

Materials: Glass, steel, bakelite, assorted metals.


Mullard Audio Output Radio Valve (or Tube) Type PM4 with glass balloon envelope. Glass surface half-silvered and half-blackened probably during manufacturing process. The Type PM4 had a tapered-tubular bulb, with bottom seal, types, polished black bakelite base and four steel B4/M base pins.

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