The DICT Development Group

  Hall-mark \Hall"-mark`\ (h[add]l"m[aum]rk`), 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.
        [1913 Webster]
  
     2. Hence, [figuratively]: A distinguishing characteristic or
        characteristics; as, a word or phrase lacks the hall-mark
        of the best writers.
        [1913 Webster +PJC]

  hallmark
      n 1: a distinctive characteristic or attribute [syn: hallmark,
           trademark, earmark, stylemark]
      2: a mark on an article of trade to indicate its origin and
         authenticity [syn: authentication, hallmark, assay-
         mark]

  105 Moby Thesaurus words for "hallmark":
     aroma, attribute, authentication, badge, banner, billhead,
     book stamp, bookplate, brand, broad arrow, cachet, cast, character,
     characteristic, check, colophon, configuration, counterfoil,
     countermark, cut, device, differentia, differential,
     distinctive feature, docket, earmark, feature, figure, flavor,
     government mark, government stamp, gust, identification, idiocrasy,
     idiosyncrasy, image, impress, impression, imprint, index, indicant,
     indicator, individualism, insignia, keynote, label, letterhead,
     lineaments, logo, logotype, mannerism, mark, marking, masthead,
     measure, mold, nature, note, odor, particularity, peculiarity,
     picture, plate, price tag, property, quality, quirk,
     registered trademark, representation, representative, running head,
     running title, savor, seal, shape, sigil, sign, signal, signature,
     signet, singularity, smack, specialty, stamp, sticker, stub,
     sure sign, symbol, symptom, tab, tag, taint, tally, tang, taste,
     telltale sign, ticket, title page, token, trade name, trademark,
     trademark name, trait, trick, verification