A monetary standard under which the basic unit of currency is defined by stated amounts of two metals (usually gold and silver) with values set at a predetermined ratio WordNet 3.0 & Open English WordNet

Bimetallism, also known as the bimetallic standard, is a monetary standard in which the value of the monetary unit is defined as equivalent to certain quantities of two metals, typically gold and silver, creating a fixed rate of exchange between them. Wikipedia

A monetary standard in economics Wikipedia Disambiguation

Monetary standard Wikidata

The use of a monetary standard based upon two different metals, traditionally gold and silver usually in a fixed ratio of values. Wiktionary

A monetary standard. Wiktionary (translation)