10 Escudos

Portugal's silver coinage was progressively debased through the mid-twentieth century, and this issue reflects that trajectory — the .680 fineness representing a step down from the earlier .835 standard used on pre-war escudo silver. The change was driven by postwar silver price pressures that made higher-purity circulating coinage economically unsustainable.

By 1969, rising silver prices forced Portugal off silver coinage for this denomination entirely, replaced by a copper-nickel substitute. Pieces from 1966 saw genuine circulation before that transition.