5 Pesos Serpiente con Craneo - 1 oz Silver Bullion

The "Serpiente con Cráneo" belongs to Mexico's Onza series, a silver bullion program that Banco de México launched in the 1980s partly in response to the peso crises of that decade — a period when dollar-denominated savings had become politically untenable and the government needed a domestic hard-asset alternative. The 1998 date places this piece in the middle of a transitional period for the series, which cycled through multiple reverse designs drawing on pre-Columbian imagery from the Aztec calendar stone.

KM#666 is notably short-lived within the sequence; the skull-and-serpent reverse was replaced after limited production runs, making mintage figures across the mid-series design changes difficult to reconcile from official records alone.