On March 10, 1976, the Postal Service issued a 13-cent Telephone Centennial stamp (Scott 1683) to honor the 100th anniversary of Alexander Graham Bell's invention of the telephone. The stamp was designed by George Tachemy based on Bell's original sketch of the first telephone.
The Bureau of Engraving and Printing produced the black, purple, and red stamp on the Giori press on tan paper as sheets of two hundred subjects, tagged, perforated 11, and distributed as panes of fifty. Mr. Zip, “MAIL EARLY IN THE DAY,” and a plate number in each corner are printed in the selvage.
Bell's notebook entry of March 10, 1876, describes his successful experiment with the telephone. Speaking through the instrument to his assistant, Thomas A. Watson, in the next room, Bell uttered these famous first words, "Mr. Watson, come here, I want to see you." The date marked not only the birth of the telephone but also the death of the multiple telegraph. The communications potential contained in Bell’s demonstration of being able to "talk with electricity" far outweighed any advantage that simply increasing the capability of a dot-and-dash system could imply.
United States Patent No. 174,465, issued to Bell on March 6, 1876, for “Telegraphy.”
Scott 2005 Specialized Catalogue of U.S. Stamps and Covers