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SPECIAL COLLECTIONS Philadelphia. National Philatelic Museum. *sca The perforation centennial, 1857-1957, the ~P957 first perforated United States stamps ... spon- .P53P sored by The 3c 1851-1857 Unit of the American Philatelic Society, July 4-6, 1957. Philadelphia, National Philatelic Museum, 1957. 232p. illus. 23cm.
1. Perforations (Philately)--U.S. 2. Postage- stamps--U.S.--Exhibitions. I. American Phila-
telic Society. “@® 3c 1851-1857 Unit. II. Title.
 
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