What this unit was
metric carat (mass) is modelled here as a weight standard of the Modern metric tradition, associated with International during Defined metric carat. The converter represents one ct as 0.2 g; its basis is two-hundred-milligrams. This is a defined or exact matrix anchor.
Its present role is chiefly comparative: it provides a stable reference for trade, craft production, taxation, bullion, and sometimes coin accounting, rather than evidence that earlier cultures used a modern definition. Coin mass is not a monetary exchange rate.
Evidence of use and sources
The working value is traceable to BIPM SI Brochure. Its record is classified as exact confidence and uses the stated basis rather than an assumed culture-wide constant.
The local library supplies contextual quotations; the linked record source remains authoritative for the modern definition.
“the ten millionth of the meridian quadrant ... be called a metre”
Standard measures of United States, Great Britain, and France, PDF p. 16. metric origin proposal
“A standard is a physical representation of a unit.”
A dictionary of weights and measures for the British Isles, PDF p. 31. standard versus unit
“the omission of necessary facts”
Standard measures of United States, Great Britain, and France, PDF p. 10. conditions required for comparison
Working definition
metric carat (mass) is represented as a Modern metric standard associated with International during Defined metric carat.
The converter uses 0.2 g per unit.
How to use it
Basis: two-hundred-milligrams; confidence: exact. A shared historical name does not make this value portable to another period or polity.
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