1961-1995, manufacturer of chemicals, aerospace equipment and electronic equipment, Bethesda, United States Martin Marietta Corporation 1961 - 1995
1931-current (2022), manufacturer of electronic equipment, London, England Multitone Electronic Company Limited 1931
active 1960s-current (2012), manufacturer of electronic equipment, Copenhagen, Denmark Brüel & Kjær (Sound and Vibration Measurement) A/S 1942
active about 1960-?, manufacturer of electronic equipment, Southend-on-Sea, England Ekco Electronics Limited