Welcome to the National Postal Museum collection of certified plate proofs (CPPs). A CPP is the last printed proof of the plate before printing the stamps. A CPP may be thought of as the “master copy” of the sheets of stamps issued to the public. Since the plate is new and the ink is fresh, the CPP is of the finest quality. Each CPP is unique, with the certifying signatures and date. For postal scholars these proofs provide important production information through the plate margin inscriptions, including guidelines, plate numbers, and initials of the siderographer, or person who created the plate from original dies or from a transfer roll.
The main body of the collection consists of CPPs of postage stamps of the United States and its territories produced by the Bureau of Engraving and Printing, dating from 1894, when the Bureau began stamp printing, to 1970. Also included are CPPs of revenue stamps, some experimental plates, and plate proofs of postage stamps produced by other printers before 1894.
More than 2,000 of the 35,000 CPPs in the collection, including the first 500 Bureau plates, have been selected for inclusion in Arago. A much smaller sample can be viewed through this presentation. The remainder of the 2,000 may be accessed by clicking here: http://postalmuseum.si.edu/ARAGOCPP/collections.html ,
or by accessing a postage stamp issue of interest. The plate proofs are best viewed under enlargement. Click on the image, then use the zoom feature to enlarge.