About the Design:

Obverse
"Estados Unidos Mexicanos" in a semicircle over the Mexican coat of arms: a Mexican golden eagle standing on a prickly pear cactus devouring a rattlesnake. At the base of the cactus there is a holm oak (encino) branch on one side and a laurel branch on the other.

Lettering: ESTADOS UNIDOS MEXICANOS

Translation: United Mexican States

Reverse
Value, Portrait of Francisco Indalecio Madero to the right

Lettering:
Mo
20c.
1977

Composition    Copper-nickel
Weight    3.02 g
Diameter    20.1 mm
Thickness    1.27 mm
Shape    Round