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I looked all over to get the various accepted value of the Planck constant since 1900. But there is never any record about the history of this mysterious number.

Qmechanic
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itsme
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    What is your question, exactly? If you are interested in the history of the measurement of Planck's constant, this question might be more suited for [hsm.SE]. – ACuriousMind Sep 14 '19 at 09:13
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    Its more than just history. The various measured values used at different times may have scientific significance – itsme Sep 14 '19 at 09:40
  • related: https://physics.stackexchange.com/questions/78684/is-it-possible-to-speak-about-changes-in-a-physical-constant-which-is-not-dimens –  Sep 14 '19 at 13:47

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I think what you are asking, in a rather poor way, is the Planck constant time-dependant over long time scales? The way you are asking this, by looking at scientific records of this measured value, is not a good approach. If you want to ask the question "are physical constants, actually constant in time?" -- which is a very good question to ask. In fact there are several experiments which want test if physical constants are actually constant; e.g. measuring the fine-structure constant $\alpha$ with atomic clocks.

However you can't compare measurements of the Planck constant through history, as they are recorded at different fractional precision. So you can't use these values to make any statement that about the Plank constant's constant-ness in time.

user27119
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  • I am exactly asking for values use at various times - – itsme Sep 14 '19 at 12:55
  • @itsme Then that's exactly suitable for the History of Science & Mathematics site. – PM 2Ring Sep 14 '19 at 13:06
  • @itsme: Please edit the question to provide the clarification. –  Sep 14 '19 at 13:47
  • @itsme for what purpose. As I have said, previous measurements would be useless to make any determination of the time varination of the Planck Constant. Also as Ben, PM and others have said, you really need to edit your question into a more useful form. – user27119 Sep 14 '19 at 16:01