This little token, with the outer legend missing, turned up among the items from the David Rogers collection. A search through all the index entries for ‘king’s head’ in Williamson brought no result, so we sent the photos to Michael Dickinson, who came up with the answer.
The one remaining question is why it was struck on a small flan or cut down.
BNS Research Blog 
The pierced cinquefoils on the reverse began to be introduced on tokens in 1664, and were most prevalent in 1665 and 1666. Cut down for use as a farthing?