U.S. 1913 parcel post stamps enjoy popularity

When first issued, these stamps were only valid for parcel post and regular postage stamps were not authorized to pay postage for parcel post mail.

U.S. Parcel Post stamps of 1912–13 - Wikipedia

United States Postal Service An American History, PDF, United States Postal Service

Scott's # Q1.

1913 U.S. Parcel Post (Postoffice Clerk) 1 Cent Stamp

1923-george-washington-booklet-stamps-rocket-flight-overprint.jpg?sfvrsn=2f510bd1_4

Histor-E Idaho State Historical Society

U.S. 1913 parcel post stamps enjoy popularity

Parcel Post Service Begins Mystic Stamp Discovery Center

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JQ2 - 1913 2c Parcel Post Due Stamp

Daniel F. Kelleher Auctions, LLC Sale - 774 Page 211

Daniel F. Kelleher Auctions, LLC Sale - 774 Page 211

The Winton M. Blount Postal History Symposia - Smithsonian