Hall-mark n.
  1. The official stamp of the Goldsmiths' Company and other assay offices, in the United Kingdom, on gold and silver articles, attesting their purity.
  2. Hence, [figuratively]: A distinguishing characteristic or characteristics; as, a word or phrase lacks the hall-mark of the best writers.
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  hallmark
       n 1: a distinctive characteristic or attribute [syn: trademark,
             earmark, stylemark]
       2: a mark on an article of trade to indicate its origin and
          authenticity [syn: authentication, assay-mark]