English: An assortment of Alnicomagnets produced by The Arnold Engineering Co. in 1956. These are probably cast isotropic Alnico 5 magnets, and show the large range of shapes manufactured for use in devices such as loudspeakers, ammeters, and small DC electric motors. Invented during World War 2, Alnico 5 was at that time the most powerful magnet in the world. It's development created a new generation of compact permanent magnet motors and loudspeakers, devices which before the war had used DC electromagnets.
Alterations to image: Cropped out surrounding ad copy.
This image is from an advertisement for The Arnold Engineering Co. without a copyright notice published in a 1956 magazine. In the United States, advertisements published in collective works (magazines and newspapers) are not covered by the copyright notice for the entire collective work. (See U.S. Copyright Office Circular 3, "Copyright Notice", page 3, "Contributions to Collective Works".) Since the advertisement was published before 1978 without a copyright notice, it falls into the public domain.
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Este trabalho está em domínio público porque foi publicado nos Estados Unidos entre 1929 e 1977, inclusive, sem um aviso de direitos autorais. A menos que seu autor esteja morto por vários anos, não é do domínio público nos países ou áreas que não se aplica a regra do curto prazo para as obras dos E.U.A, como o Canadá (50 apm), China (50 apm, com exceção de Hong Kong e Macau), Alemanha (70 apm), México (100 apm), Suíça (70 apm), e de outros países com tratados individuais. Veja esta página para mais explicações.