(n.) A seal, as of a letter.

aroma attribute badge billhead book stamp bookplate brand broad arrow cast character characteristic check colophon configuration counterfoil countermark cut differentia differential dignity distinction distinctive feature docket earmark feature figure flavor government mark government stamp gust hallmark identification idiocrasy idiosyncrasy importance impress impression imprint index individualism keynote label letterhead lineaments logo logotype mannerism mark marking masthead mold nature odor particularity peculiarity plate prestige price tag prominence property quality quirk registered trademark running head running title savor seal shape sigil signet singularity smack specialty stamp sticker stub tag taint tally tang taste ticket title page token trade name trademark trademark name trait trick