Écu

The écu (Tristanian: écu) is the currency of Tristain. The subunits of écu are the sou and denier; one sou equals twelve deniers.

It is likely, since this was the currency of France, originating in 1266, that:

1 écu = 6 livres

1 livre = 20 sous

1 sou = 12 deniers

However, this is simply speculation.