My pieces

I have two of them, one marked "758" with pen on glass, second "926". They have about 350KΩ without heating and ca 60kΩ when 1V was applied to heater. But heater current is much higher - 0.5A at 1V

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Hello Mr. Szczesniak,

these are interesting news. 

I have a question: Did they have markings on the top from the bulbs? The in rm.org shown example is marked with ink: 40Z.

Thank you and best regards  H.-T. Schmidt

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Yes. This one with '758' marking has 'Hg', second is '7SH', but im not sure if I correctly recognized letters

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Thank you for looking. Unfortunately, it is not possible to derive a type designation here. The variance is too great.

Best regards  H.-T. Schmidt

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