One peculiarity of the harp is that it bears a semi-nude winged female figure on the pillar, a feature which became common on English coins beginning in the second quarter of the 17th century.
The obverse of the smaller copper halfpenny shows Saint Patrick dressed in bishop's garments wearing a mitre and holding a double-cross crozier.
The splash of brass on the obverse of the copper coins is intended to create the illusion that the royal crown that King David glances at is made of gold.
The current thinking is they were minted between 1646 and 1660 before the official reign of Charles II of England, while he was in exile, due to new documents recently discovered by John N. Lupia and published in the C4 Newsletter 2008. Who coined them and the circumstances surrounding them is still uncertain.
In 1681 it is supposed that Mark Newby, a Quaker who emigrated from Ireland, had brought a substantial quantity of these copper coins to North America when he relocated to West New Jersey, settling in Camden.
The die varieties for the larger coin have been completely documented by Dr Roger Moore, Stanley E. Stevens and Robert Vlack, in the Colonial Newsletter 2005.