***Envelope Privy Mark***
On 22 August 1872, the Overland Telegraph line between Adelaide and Darwin was finally connected. It was the result of years of planning and 23 months of arduous construction through the arid centre of the continent and  the wet, mosquito-infested terrain of the Top End. The telegraph involved 36,000 poles across 2,839 kilometres, from Port Augusta in the south to Darwin in the north, through territory virtually unexplored by Europeans. This huge logistical achievement has been called the greatest  engineering feat of the 19th-century Australia.
 
This coin features an 'Envelope Privy Mark', the thirteen cities and towns on the Overland Telegraph Line and includes a Morse code message 39,000 poles and 2,839 kilometres – the length of the line and the number of poles it took to construct the line. The anniversary date of the Telegraph Line – 1872 to 2022 – is also written in Morse code. 
Mintage 7,500