"The Scott United States Specialized Catalogue is the leading U.S. catalogue in the world. There are hundreds of thousands of price changes every year and it is essential for collectors to have the most recent issue. NEW this year, we are expanding our listings and back of book area. The Scott US Specialized cover includes a value for every stamp produced in the U.S. in addition to covers, revenues, duck stamps and more. The numbering system used by Scott to identify stamps is dominant among stamp collectors in the United States, Canada and Mexico and throughout the world"--