A post office purchase involves several items, including a PANE, STAMP, MAILER, COIL, stamps, SHEET, and boxnumber. A PANE is a small window or section of a larger window, usually made of glass. A STAMP is a small adhesive paper that is used to indicate payment of a fee or tax. A MAILER is an envelope or other container used to send mail. A COIL is a roll of stamps. Stamps are also small adhesive papers used to indicate payment of a fee or tax. A SHEET is a large piece of paper, usually rectangular in shape. A boxnumber is a unique identifier assigned to a post office box.