U.S. 1928-31, Architecture Commemorative Stamps, USPS Souvenir Page. First Day of Issue Aug 28, 1981, Washington DC 20013. This page is fresh very fine condition. Scan is an example. Never folded, shipped flat in a sheet protector.
USPS Souvenir Pages or American Commemorative Cancellations are -Official First Day of Issue Cancellations, which are a mint stamp or stamps affixed to an 81/2x101/2 color page, and include technical and historical information about the stamp or stamps and the designer. The pages were issued flat and unfolded.