Down the rabbit hole again! I've started to investigate the dies used to produce the 1787 sixpence with the intention of collecting one example of each die (over time). In the past three days I've built a data base of images from 171 examples, hopefully with many more to come. My target is 500 sample images and I hope this isn't optimistic.
Here are a few preliminary observations about the reverse dies. There are four primary families of dies:
With semee of hearts in Hanoverian Shield and without serifs on the "7"s in the date
With semee of hearts in Hanoverian Shield and with serifs on the "7"s in the date
Without semee of hearts in Hanoverian Shield and without serifs on the "7"s in the date
Without semee of hearts in Hanoverian Shield and with serifs on the "7"s in the date
In the overwhelming majority of instances the Hibernian harp contains 6 strings. However, I've come across the following:
A. 5 examples of with-hearts/without-serif-7 coins that have 7 strings (just under 3% of sample to date)
B. 3 examples of without-hearts/without-serif-7 coins that have 7 strings (about 1.8% of sample)
C. 1 example of with-hearts/with-serif-7 coin that has 7 strings (about 0.6% of sample)
All of the examples in group A belong to the same die. At least 2 examples of those in group B are from the same die, while the jury is out on the third example. I strongly suspect that all coins in groups A and B are from the same die. My reasoning? Firstly, the absence of the semee-of-hearts was a mistake recognised and rectified part way through the run. As with the shillings, the hearts were hand-engraved, presumably on existing dies, to correct the error. There are about three die flaws that you can see developing across the coins in groups A and B, becoming more obvious as the die ages: Die fill in two letters and the wearing of the left lower serif in "1" of the date.
I'm noticing generally much more die wear on 1787 sixpences than on 1787 shillings. Given that a similar quantity of each denomination was struck, I suspect that there were, perhaps, significantly fewer dies used. This is just a hunch. I'll see if can find any records indicating the number of dies produced as this information is available for the shillings. The number of dies produced needn't be the same as the number of dies used, though.
Further updates to come.