Agio (Italian aggio) is a term used in commerce for exchange rate, discount or premium.
The variations from fixed par values or rates of exchange in the currencies of different countries.
[1] The term was also used to denote the difference in exchange between two currencies in the same country where silver coinage was the legal tender.
An agio was sometimes allowed for payment in the more convenient form of gold or where the paper currency value of a country fell below the bullion that it ostensibly represented.
Reflecting their nominal value, 100 sovereigns in England would be accepted as a payment in full for £100 debt.