Agio

1989, Isaac Levy, translator, The Pentateuch (translation of, Samson Raphael Hirsch, Der Pentateuch, ubersetzt und erlautert), second edition, volume 2, Exodus, Judaica Press, →ISBN, page 582 (commentary to Exodus 30:16), Owing to the enormous number of half-shekel coins required each year in Adar, these were greatly in demand, and the money-changers made a small fixed charge of an agio for changing whole into half shekels.

Source: wiktionary

The money of such banks being better than the common currency of the country, necessarily bore an agio, which was greater or smaller, according as the currency was supposed to be more or less degraded below the standard of the state.

Source: wiktionary