a certificate from a recognized authority attesting to the genuineness of a philatelic item.  Also see <#expert=expertization>.

service for a fee that provides evidence of mailing.  Certificates of Mailing were first made available in 1915.

service for a fee that provides a mailing receipt and maintenance by the <#usps=USPS> of a delivery record.  Certified Mail requires the signature of the recipient.  First offered in 1955.

a stamp issued in 1955 to pay the fee for <#certmail=Certified Mail>.  <#scott=Scott> FA1.

the bits of paper removed in the <#perf=perforating> process.