see <#aps=American Philatelic Society>.

private printer of the 1968 6¢ Walt Disney <#commem=commemorative>,  <#scott=Scott> 1355.

see <#rr=Return Receipt>.

a <#cachet> added to a <#fdc=first day cover> subsequent to its <#cancel=cancellation>.

a letter which was advertised in a newspaper by the post office in an attempt to induce the addressee to claim it. Advertising of letters ended in the early 1920s.