Summary: are used by high volume mailers who presort their mail for the USPS and get discounted rates as a result In the good old days a precancel was a stamp with a cancel applied by the USPS usually just bars or a city name and bars The USPS still uses the term precancel but today the stamps no longer have a cancel applied and are more properly called service inscribed
Image Dimensions: 884 x 646
Image originally found here.