The circled A is a symbol so widespread, so widely recognised and disseminated that it has come to be taken as a traditional symbol of anarchism, seeming to have existed forever.
The circled A at 60 part three: The true story

The circled A is a symbol so widespread, so widely recognised and disseminated that it has come to be taken as a traditional symbol of anarchism, seeming to have existed forever.
Despite well-documented evidence of its origin, numerous fanciful speculations persist, including within anarchist circles and many libertarian historiographies that explore the symbol’s origin.
Tomás Ibáñez gives first-hand testimony on the origins of the famous anarchist symbol, first proposed in April 1964
The circled A was invented in Paris in 1964 and reinvented in Milan in 1966