in 1939, the company's offerings included carbon, condenser, crystal, and dynamic microphones. Wired and wireless microphones together represent the largest category of Shure's overall business. Shure currently produces numerous series of microphones for various applications, including the SM, Beta, KSM, and PG series, as well as specialty consumer microphones, Microflex, and Easyflex (conferencing systems for commercially installed applications). One of Shure's most visually iconic microphone series is the Unidyne series, seen in use by heads of state and popular recording artists and performers from the 1940s through the end of the twentieth century, including President John F. Kennedy, Ella Fitzgerald, and Frank Sinatra. The Model 55 Unidyne is pictured with Harry S. Truman in the photograph where he is holding the Chicago Tribune newspaper with the erroneous front-page headline "Dewey Defeats Truman". It is also pictured in front of Fidel Castro on the cover of the January 19, 1959, issue of Life magazine and in front of Martin Luther King Jr. as he delivered his "I Have a Dream" speech during the August 1963 March on Washington for Jobs and Freedom. The original Shure 55 Unidyne microphone was designed by engineer Ben Bauer and first produced in 1939. Shure designed the 55 Unidyne as a rugged public address microphone with good audio performance. It was notable for its single-element, unidirectional design, which was smaller, less susceptible to feedback, and less sensitive to ambient noise than other microphones of the time. Several variants of the original Unidyne have been produced, most notably the 55S or "Baby Unidyne". The 55S is sometimes referred to as the "Elvis mic" due to its frequent use by Elvis Presley, and is the microphone depicted with Elvis on the commemorative first-class Elvis stamp issued by the U.S. Postal Service in 1993. In 2008, the Unidyne Model 55 microphone was inducted into the TECnology Hall of Fame, and the following year, Shure released the 55SH Series II. A supercardioid version, the Super 55 Deluxe Vocal Microphone, was introduced in 2009, featuring high gain before feedback and excellent off-axis rejection and further extending Unidyne's 70-plus year legacy. The 55 Series microphones were given the "IEEE Milestone" award in 2014. With the U.S. Army's approval of the Shure T-17 microphone for use during World War II, Shure began producing what would be several specialized microphones for U.S. military use during that war. Shure's adoption of the Military Standard Specification,