A block of four 20-cent commemorative stamps honoring American inventors Charles Steinmetz, Edwin Howard Armstrong, Nikola Tesla, and Philo T. Farnsworth was issued September 21, 1983, in Washington, DC. The First Day of Issue ceremony was held at the US Patent and Trademark Office in Arlington, Virginia.
The US Patent and Trademark Office houses the National Inventors Hall of Fame, which was established in 1973. Three of the men featured on the block of four stamps had, at the time of the issuing of the stamps, been inducted into the Inventors Hall of Fame — Tesla (1975), Steinmetz (1977), and Armstrong (1980).
Each stamp in the block of four, designed by Dennis Lyall of Norwalk, Connecticut, and modeled by Clarence Holbert, features a portrait of one of the inventors and a representation of one of his significant inventions. All four men were electrical engineers.
The stamp was printed in the offset/intaglio process. There are fifty stamps per pane.
Postal Bulletin (August 18, 1983).