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 timesthe 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 definedrange. 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 andpass 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 thediameter 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 diameterof the Dump very precisely.

To read the complete article, see:
The Way Henshall Cut and Struck the 1813Dump / Fifteen Pence Impacted the Viability of the Holey Dollar(https://www.sterlingcurrency.com.au/research/way-henshall-cut-and-struck-1813-dump-fifteen-pence-impacted-viability-holey-dollar)

Holey dollar is the name given to coins used in the early history of two British settlements: Prince Edward Island (now part of Canada) and New South Wales (now part ofAustralia). The middle was punched out of Spanish dollars, creating two parts: a small coin, known as a "dump" in Australia, and a "holey dollar". This coinwas one of the first coins struck in Australia.

To read the complete article, see:
Holey dollar (https://en.wikipedia.org/wiki/Holey_dollar)