1) a <#label> applied by the Post Office to "seal" mail, which was opened either intentionally, or by accident. Post Office Seals were supplied to larger post offices and have <#scott=Scott> numbers prefixed with OX. Typeset Seals were privately printed for sale to Fourth Class post offices and have Scott numbers prefixed with LOX. 2) a <#label> such as a <#christmas=Christmas Seal>.