Hallmark

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early 18th century (as a noun): from Goldsmiths' Hall in London, where articles were tested and stamped with such a mark.

wiktionary

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1721. hall +‎ mark, from Goldsmiths' Hall in London, the site of the assay office, official stamp of purity in gold and silver articles. The general sense of "mark of quality" first recorded 1864. Use as a verb from 1773.

etymonline

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hallmark (n.)

1721, official stamp of purity in gold and silver articles, from Goldsmiths' Hall in London, site of the assay office; see hall + mark (n.1). General sense of "mark of quality" first recorded 1864. As a verb from 1773.