sentences:  After reaching the letter "H", this practice was discarded in favor of simply indicating the class of postage (e.g., first class) for which the stamp was intended.In 2006, the United States Postal Service applied for permission to issue a stamp similar to non-denominated stamps in the US, termed the "Forever® stamp", for first-class postage.On March 26, 2007, the United States Postal Service unveiled the first such stamp, which went on sale April 12, 2007, for 41 cents (US$0.41), the so-called "Liberty Bell" stamp, which is marked "USA FIRST-CLASS FOREVER".