Penny or rather shilling has dropped.
Letter from Prince Rupert to Sir William Neale, commander of the Hawarden garrison from 3rd December 1643 to the end of the war, saying £100 for the provision of armies and ammunition for Col. Marrow (died 21st August 1644) and the victualising and furnishing of Hawarden Castle gives an inadvertent bonus. Although it doesn't specifically state that coins were struck at Hawarden, it certainly makes it a centre for the receipt of funds, be they cash or plate, and where the plate goes, the dies will follow. Allen shilling obv. B has a bird as the obverse mark. If the bird shillings were struck in conjunction with the instructions outlined in the letter, it likely limits the dates to 3rd Dec. 1643 - 13th March 1643/4, end of March - 15th May 1644 or 25th July to 20th August 1644. The first period would be in line with refurbishing the castle following its recapture, the second covers a period when Rupert was in Oxford, and so is the least likely, whilst the last period saw Rupert camped on the Welsh side of the Dee at Chester (so 4 miles from Hawarden), and actively recruiting at this point to replace the troops lost at Marston Moor. Outside these dates either Neale or Rupert or both were otherwise occupied elsewhere.
A happy coincidence is that the arms of Flintshire are a cross with a bird in each angle. Given the use of the leopard head (Shropshire & Shrewsbury), gerb (Cheshire & Chester), tower (Worcester) and pear/pears (if the HC is a Worcester(shire) location), then it is a logical fit that the bird should represent Flintshire. Options are likely Hawarden, Flint, Mold, Rhuddlan or one of the ports used for landing troops, but Hawarden is closest to Chester where we know there was a rocker press available. The shilling is paired with 3 marked reverses - rev. 6 Boar's Head, rev. 7 Scroll(?), this mark is uncertain and rev. 8 lis. Trouble is that there may be no more than half a dozen examples of obverse B across all marks, making hard work establishing a chronology for the pairs.
It makes sense in terms of timing, as Rupert was trying to raise troops from the area in July/August 1644 after his return from York and the boar's head appears on a reverse paired with the early halfcrown obv.I and the second reverse on the sixpence which post-dates the tower both sides die pair, which I believe were struck before the end of the first week of July 1644. It also leaves open the possibility that the lion used as a reverse mark on a couple of shillings and a half-crown reverse is significant, as is the boar's head mark seen on a few reverses. Denbighshire(?) for the first, or maybe the mark of Edward, Lord Herbert, who was granted a commission on 29th July 1644 to strike denominations current in the realm at an unspecified location (though almost certainly given in conjunction with his commission to raise 10000 troops from the Irish Confederates. The family arms bear three rampant lions on a halved blue and red spade shield. Similarly, the arms of Radnor have a boar's head in each quarter, though the possibility of a North Wales coat of arms hasn't been excluded. All this does nothing to show the HC halfcrown was struck at Hawarden, but at least it moves the shilling question forwards. The real bonus would be the creation of another box to fill.
I can feel a trip to both Ruthin and Llandrindod Wells record offices coming on.