publication on Aethelred coin from the Fitzwilliam Museum
Those who are able to examine such coins may well notice a small scar or groove incised in the surface of some of them. These are known as 'peck' marks and embue such coins with some of the drama of Aethelred's reign. Vikings had the habit of digging the point of their daggers into coins to assure themselves that they were of solid silver.
See publication Saxon and Vikings (the mint)