{
  "schema_version": 1,
  "series_id": "codata-precision-control",
  "retrieved_at": "2026-08-20",
  "source": {
    "schema_version": 1,
    "retrieved_at": "2026-08-20",
    "provider": "National Institute of Standards and Technology",
    "documentation_url": "https://physics.nist.gov/cuu/Constants/",
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      2002,
      2006,
      2010,
      2014,
      2018,
      2022
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      "muon-electron mass ratio",
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      "electron g factor"
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    "robust_companion": "Median relative standard uncertainty across the same constant set.",
    "date_rule": "CODATA adjustment year, represented as 31 December of that year.",
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