noun (n)

• an indication of approved or superior status(noun.communication)

  Synonym:
  seal, seal of approval
  

  source: wordnet30
• a warrant formerly issued by a French king who could warrant imprisonment or death in a signed letter under his seal(noun.communication)

  Synonym:
  lettre de cachet
  

  source: wordnet30
• a seal on a letter(noun.artifact)

  source: wordnet30
• A seal, as of a letter.(noun)

  source: webster1913