The postal system handles millions of pieces of mail each day. Many of these items are single pieces of correspondence, such as bills, checks, photos and personal letters. But a very significant number are associated with promoting or advertising products or events or organizations. Most often, the exact same promotional material is sent to hundreds, thousands or even tens of thousands of recipients. The US post office offers special postal rates for these mailings. Generally, the sending organization is responsible for sorting the mail in a manner that minimizes the efforts required by the postal system. It must also be labeled, and often coded in pre-determined ways. A primary requirement is that the number of pieces be very accurately known since the post office charges for each piece sent. The weight of an individual item must be determined, the total weight [+]