In the early modern period, it was necessary in Europe because at that time coinage had an intrinsic value and even though a town was besieged commerce had to continue and soldiers had to be paid.
Not sure as to why the shape, might be ease of manufacture or somesuch.
Money minted during a siege.
https://en.wikipedia.org/wiki/Siege_money
Not sure as to why the shape, might be ease of manufacture or somesuch.
For some reason I thought it was the besiegers that needed this