The first gold coin ever found has been uncovered at Vindolanda. Although it was found in the late fourth century level, it is an aureus of the Emperor Nero. From the press release:
The Roman site of Vindolanda, with an active archaeological research programme which has been ongoing for 43 years, is used to remarkable discoveries – notably the world famous Vindolanda writing tablets which hold the title of Britain’s top archaeological treasure.
With a vast array of finds from 300 years of Roman occupation on this site the discovery of a gold coin had previously alluded 2 generations of archaeologists, that was until 3rd June 2014.