Compare Front Views of Eagle

Arras (snake)	Mexican Coin Design	Arras (branch)

A similar design has been used on Mexican coins since the 1800's, but designs similar to this were used starting in 1905. It was replaced by the side view of eagle design about 1945.

Note the the Arras design on the left is very similar to the coin, with a snake in the eagle's beak. The Arras design on the right is generally similar, but the eagle is holding a branch rather than a snake.