The Hammarlund Manufacturing Company was founded by Oscar Hammarlund in New York City, New York, United States, in 1910. When the company was dissolved in 1973, it was among the United States' very oldest producers of radio equipment. History. The first Hammarlund plant was a loft operation engaged in radio component manufacturing on Fulton Street in Lower Manhattan, New York City. Their variable capacitor designs quickly became industry standards, and the component's schematic symbol was adopted as the company's logo.
https://en.wikipedia.org/wiki/Hammarlund