the impression made by the post office or authorized mailer on a <#cover>, typically indicating the date, time and place of mailing. Postmarks may be made by <#machcancel=machine> or <#handstamp>. Postmarks are most commonly circular, but are also found as ovals, boxes, straight lines and <#sprayon=spray ons>. While postmarks are not <#cancel=cancels>, they are sometimes used for that purpose, and the two terms are often and incorrectly used interchangeably.