The innovation of coinage is to standardize the unit mass and value, i.e. to create easily usable units. The specific image on the coin authenticates the mass a

The innovation of coinage is to standardize the unit mass and value, i.e. to create easily usable units. The specific image on the coin authenticates the mass and value given to the unit. This is an UX improvement over using different shapes (jewelry or other non-standard gold pieces) as money, which need to be weighed every time you trade. Gold was used as money before coinage.