Depicts the seal of the United Mexican States.

The Seal of the United Mexican States is a modified version of the national coat of arms, with the addition of the full official name of the country Estados Unidos Mexicanos, in a semi-circular accommodation in the upper part of the seal. Current and past Mexican peso coinage have had the seal engraved on the obverse of all denominations.

The coat of arms depicts a Mexican golden eagle perched on a prickly pear cactus devouring a rattlesnake. To the people of Tenochtitlan this would have strong religious connotations, but to the Europeans, it would come to symbolize the triumph of good over evil (with the snake sometimes representative of the serpent in the Garden of Eden).

At the center, the image of the obverse of a cob type colonial Mexico coin, 8 Reales 1608 (KM# 44), Philip III of Spain; at the upper side, parallel to the coin frame, the legend NUMISMATIC HERITAGE OF MEXICO; on the left side, the Mexican mint mark, while on the right field is the $100.

Cobs are the original treasure coins. Struck and trimmed by hand in the 1500s through 1700s at Spanish mints in Mexico, Peru, and Colombia (among others), silver and gold cobs are handsomely crude, nearly all with a cross as the central feature on one side and either a coat-of-arms (shield) or a tic-tac-toe-like "pillars and waves" on the other side. Silver cobs are known as "Reales" and gold cobs are known as "Escudos," with two 8 Reales (about 27 grams each) equaling one Escudo. Some cobs were struck with a date, and most show a mintmark and an initial or monogram for the assayer, the mint official who was responsible for weight and fineness. Size and shape were immaterial, which means that most cobs are far from round or uniform in thickness. Cobs were generally accepted as good currency all around the world due to the purity of their metal (0.930), and were the exact coins pirates referred to as "pieces of eight" (8 Reales) and "doubloons" (any gold cobs but originally 2 Escudos).