The Libertad series was introduced in 1982 as Mexico's official silver bullion program, but the fractional denominations took years to reach production. The half-onza was being evaluated in the late 1980s alongside other fractional sizes, and 1990 pattern pieces exist documenting that evaluation process before the denomination entered regular circulation. Patterns from this program are rarely cataloged with any consistency — the Mexican Mint did not publicize trial strikings, and survivors surface almost entirely through the secondary market rather than official records.
The Libertad series was introduced in 1982 as Mexico's official silver bullion program, but the fractional denominations took years to reach production. The half-onza was being evaluated in the late 1980s alongside other fractional sizes, and 1990 pattern pieces exist documenting that evaluation process before the denomination entered regular circulation. Patterns from this program are rarely cataloged with any consistency — the Mexican Mint did not publicize trial strikings, and survivors surface almost entirely through the secondary market rather than official records.