1 Peso Pattern, Guerrero Águila, Brass

Pattern coinage from the Casa de Moneda de México in this period reflects an intensive internal evaluation of alloy substitutes driven by rising silver and base metal costs. By 1980, the circulating 1 Peso had already been debased through successive reformulations, and the mint was actively testing brass alternatives before settling on stainless steel for the denomination's final years before the 1993 redenomination wiped it from circulation entirely. The Guerrero Águila designation distinguishes this as a regional eagle type specific to Guerrero state issues — a design lineage with roots in earlier Mexican coinage rather than the federal arms.

Patterns of this type were struck in very limited quantities for internal review and rarely escaped official channels.