Lead Isotope Ratio

鉛同位体比 ／ lead isotope　—　Research

The fingerprint of lead contained in metal, which differs by place of origin.

Lead has isotopes with different masses, and their ratio varies from mine to mine. By comparing the lead isotope ratio in a coin with the values from various mines, one can narrow down the source of the material.

⚠ The official history Shoku Nihongi records that the copper for the Wadōkaichin was presented from Chichibu, but the lead isotope ratios of many extant specimens match those from the Nagatō copper mine in Nagato Province or Zōmeki in Suō Province. "The fact that a presentation was recorded" and "the source of copper used for mass production" are separate questions; what is written and what can be found through investigation can be verified independently.