The island had long relied on gold for currency—but around 660, its economy was flooded with silver coins. The influx created an economic boom, stimulating trade and boosting urban development.

Some of the coins were English silver groats, minted by both Henry V (ruled from 1413 to 1422) and Edward IV (ruled from roughly 1461 to 1483), while others were Scottish gold demy and half-demys, ...