The double headed eagle is the heraldic arms of Richard, Earl of Cornwall and Poitou, younger brother of Henry III. Richard was elected King of the Romans in 1257 and it was at this time that he took the double headed eagle as his personal device. The weight post dates this event.

In 1244 he recieved from his elder brother the right to influence the new coinage and this control of the mint might be presumed to indicate some additional authority over weight and measures.