I got one for my collection recently - https://www.cointalk.com/threads/25-pesos-olimpiada-mexico-silver-1969.293408/
As I recall, the legend was when the Aztecs were looking for a homeland they were told (by a god I presume) to look for a sign of an eagle perched on a cactus eating a snake. They saw it, and that was where they built Tenochtitlan, which later became Mexico City.
