By far the most common Charles I threepences were produced at the Aberystwyth mint between 1638 and 1642.
Coins were produced at the Oxford mint between 1644 and 1646, using the Aberystwyth dies for the obverse, while the reverse of the 1644 coin shows the Declaration of Oxford in three lines: - The religion of the Protestants, the laws of England, the liberty of Parliament.