The Way Henshall Cut & Struck the 1813 Dump/Fifteen Pence Impacted the Viability of the Holey Dollar

Whenever Australia’s first coins are discussed, most of the focus is placed on the Holey Dollar rather than the Dump. This is hardly surprising, as the larger coin had four times the purchasing power of the smaller coin.

What is often overlooked in that assessment is the fact that the way the Dump was cut and struck determined whether both coins remained in circulation.

If Macquarie’s counter-stamping plan was to prevent coins from being taken outside NSW, the weight of both the Holey Dollar and the Dump needed to fall within a tightly defined range. If either coin weighed outside their intended range, its silver value could vary widely from its face value, which could be an incentive to take the coin away from NSW and pass it off at its intrinsic value, defeating the purpose of the whole exercise.

All other criteria being equal, the weight of each Dump (and thus the weight of each Holey Dollar it was cut from) was determined by the diameter of the Dump. The larger the diameter of a Dump, the heavier it is; and also the lighter the Holey Dollar it was cut from.

If the weight of each coin was to be within a tolerance that enabled the currency value of both coins to exceed its intrinsic value, Henshall needed to calculate the diameter of the Dump very precisely.

The question then becomes, just what diameter would a Dump need to be before it was at risk of being exported for its intrinsic value? Further, could a Dump be cut so small that the resulting Holey Dollar had an intrinsic value greater than its currency value?

A further interesting question is that although the diameter and weight of each Dump and Holey Dollar still in existence has not been exhaustively recorded (at least, such data has not yet been published), there is some thought that Henshall may have adjusted his calculations regarding the optimum diameter of each Dump over the time he was producing them.

Published results of an exhaustive study of the diameter and weight of these coins could well have consequences for our understanding of which Dumps were struck first.

Diameter = Weight = Striking Sequence?

The numismatist that has studied the Dump in the most detail is undoubtedly Bill Mira, he unequivocally stated that “Neither the diameter nor the weight has any relation to the dies used. Diameters vary from 18-20mm, whilst the weight averages 83 grains.[1]”

Based on his survey of over 200 Dumps, Mira theorised that dies C/4 may have been used first, followed by dies E/3, then A/1 and finally D/2. Based on their crude appearance, Mira supposed that dies C/4 and E/3 could have been “…trials and were used initially on only a few pieces[2]…”

If a systematic study of the weights is published, and if Dumps featuring the the C/4 and E/3 dies are shown to have marginally wider diameters (and/or are marginally heavier) than those struck with the A/1 and D/2 dies, it may reinforce Mira’s hypothesis that the first two pairs of dies were phased out not as a result of their aesthetic characteristics per se, but as a result of the likelihood that they would strike coins with the correct diameter.

Just half a millimetre difference in the diameter of a Dump corresponds with an increase in weight of around 5%, so any changes made may not have been observable at the time of Mira’s research.

The Queensland numismatist George Snelgrove has also given some thought to the relationship between the diameter of a Dump, its weight and the viability of Macquarie’s exercise.

Dump 20% and Holey Dollar 80%

In an article in the 2010 Report of the Australian Numismatic Society, Snelgrove points out that as the total declared face value for the coins was 75 pence / six shillings and threepence (five shillings for the Holey Dollar and one shilling threepence for the dump), the relative proportions of the total silver weight and surface area across both coins would need to reflect the proportion of the total currency value that each coin was intended to have.

“When Governor Macquarie ordered the Dollars to have a plug struck from their centre he would have required it to be 20% of the Dollar's weight, arrived at as follows; Each 8 Reales dollar became a Holey Dollar and Dump, which then had a combined value of six shillings and threepence (i.e. 75 pence). Each Dump of fifteen pence, therefore was 20% of this total value. On this basis, the Dump should have been 20% of the size and weight of the coin from which it was struck.[3]”

“The surface area of a 40 mm 8 Reales is 1,257 mm, so 20% of this is some 251 mm. The surface area of an 18 mm Dump is 254 mm, confirming that the centre punched out was almost exactly the targeted size. It has been pointed out by Bruce Canning, of the Canning Mint, that the diameter of the punch for an 18 mm Dump was, likely to have been eleven sixteenths of an inch (Imperial), which is slightly under 18 mm, but when over struck with the dies for the fifteen pence the planchet would have spread to 18 mm.[4]”

“However, the degree of the expansion would have depended on the thickness of the planchet and the pressure of the overstrike. The 19 mm Dumps that are known may well reflect a slightly thicker planchet and the application of greater pressure in the strike. Turning now to the extremely small number of Dumps known that are 20 mm in diameter; their surface area is 314 mm or 25% of the full 8 Reales coin. Clearly, this was not the result that Macquarie wanted, as it would make the export of such heavy Dumps much more attractive to traders. Probably the very small number of 20 mm Dumps reflects the fact that Macquarie realised that these were too heavy and early on ceased their production in favour of the smaller 18mm.[5]”

Mira states that the heaviest Dump he had sighted had been struck with the D/2 die pair, which in his mind was most likely to have been the final die pair used. If that is the case, any variance in diameter may be a function of chance rather than design. Despite this single coin, the relationship between weight, diameter and the order in which these coins were struck will be interesting to pursue further.

A Combined Currency Premium of 30%

Although the currency ratio between the Holey Dollar and the Dump is indeed 80/20, the two coins had a combined currency value over their intrinsic value of around 30%, which effectively provided Henshall with a reasonably wide margin for cutting and striking the coins before they were at risk of being exported. The table below shows the relationship between the weight, diameter and currency (face value) of a range of Dumps and Holey Dollars.

The Relationship Between Diameter, Weight and Face Value for the 1813 Holey Dollar and Dump

Mira has stated that a Dump with a diameter of 20mm is at the upper range of the 200 coins he studied, however the intrinsic value of such a coin would still remain 13% below its currency value - well below the level one would expect it would need to be for it to be at risk of being exported.

As can be seen from the data above, if the standard weight and thickness of an 8 reales is accepted as constant, it is only when the diameter of a Dump reaches 21.5mm that its weight exceeds the currency or face value of 15 pence. Mira’s published research after a survey of 200 coins does not include any reference to a coin weighing anywhere near 7.82 grams.

Mira stated that the single heaviest dump he had seen by 1974 weighed 6.61 grams,[6] which at an intrinsic value of 12.69 pence, was still 15% below the currency or face value that the coin had, presumably sufficient disincentive to export the coin. Mira also stated that this Dump had been struck with the D/2 die pair, which does not indicate that Henshall was likely to have adjusted the diameter of the Dump over time.

If we examine the weight and intrinsic value of the Holey Dollars with an internal diameter corresponding with the diameter of most known Dumps, we can see that all had a currency value at least 30% above their intrinsic value, so none were at no risk of being exported on that basis.

Although it is highly unlikely any Dumps weighed enough to warrant them being exported, it will be interesting to further test whether Macquarie and Henshall did indeed slightly reduce the intended diameter of the Dump over time, to minimise the possibility that any Dump might weigh outside the intended range.

Until then, the above consideration of weights, diameter and currency value demonstrates that the calculations by Macquarie and Henshall were adequate for the task of ensuring the NSW 1813 Dumps and Holey Dollars remained in circulation within NSW.

Endnotes:

[1] Mira; Bill, ""The New South Wales Dumps"", The Metropolitan Coin Club of Sydney, Sydney, 1990, p 4.
[2] Mira; Bill, ""The New South Wales Dumps"", The Metropolitan Coin Club of Sydney, Sydney, 1990, p 19.
[3] Snelgrove; George, ""Holey Dollars and Dumps of NSW - Some Further Comment"" in the The Report of the Australian Numismatic Society, 2010, p 10.
[4] Snelgrove; George, ""Holey Dollars and Dumps of NSW - Some Further Comment"" in the The Report of the Australian Numismatic Society, 2010, p 10.
[5] Snelgrove; George, ""Holey Dollars and Dumps of NSW - Some Further Comment"" in the The Report of the Australian Numismatic Society, 2010, p 10.
[6] Mira; Bill, ""Lachlan Macquarie’s NSW Dump"" in The Report of the Australian Numismatic Society, 1974, p 10.