US Stamp Price Scott Cat. # Q1: 1913 1c Parcel Post
Big Blue 1840-1940: Italy-Special Delivery, Postage Due, Parcel
Robert A. Siegel Auction Galleries, Inc. Sale - 1060 Page 1
Would You Consider This An Airmail Stamp? - Stamp Community Forum
Back-of-the-book issues are always suitable for any collection
US Stamps #Q1-Q3 Parcel Post Mint OG NH VF/XF LOT #84257*
U.S. Parcel Post Stamps Archives - Jamestown Stamp Company, Inc.
Collecting U.S. Postage Stamps
Q1 - 1912-13 1c Parcel Post Stamp - Post Office Clerk - Mystic
El Salvador's 1895 parcel post set