sentences:  In addition, three Airmail Special Delivery stamps were issued in the 1930s, two regular ones and an imperforated issue specially produced by Postmaster General James Farley.In used condition none of the special delivery stamps are particularly scarce.On June 7, 1997, the United States Postal Service terminated Special Delivery mail service which left many unused Special Delivery stamps in circulation that were no longer valid for such postage.