On January 17, 1976, the 13-cent Interphil stamp (Scott 1632) was issued in anticipation of the Seventh International Philatelic Exposition—Interphil '76—to be held in the U.S. Interphil '76 was the first international philatelic exhibition held in America since SIPEX at Washington, D. C., in May, 1966. An officially recognized event of the American Revolution Bicentennial Authority, Interphil ’76 was appropriately hosted May 29 through June 6, 1976, in Philadelphia, Pennsylvania, the city in which the Declaration of Independence and the U.S. Constitution were written.
The stamp was designed by Terrence McCaffrey, lithographed in dark blue and red, and engraved in ultramarine and red on the Giori press. It was printed on sheets of two hundred subjects, tagged, and perforated 11, and distributed as panes of fifty. Mr. Zip, “MAIL EARLY IN THE DAY,” and a plate number (in each corner of the sheet) are printed in the selvage.
Scott 2005 Specialized Catalogue of U.S. Stamps and Covers
The United States Specialist, May 1976