Enthusiasts lined the front of the Royal Mint to have a glimpse of the new effigy.

Unveiled on a large round poster, the new effigy will switch directions. King Charles III faces to the left while his mother, the late Queen Elizabeth II faced to the right.

The last time Australians had a different monarch on their coins was in 1953, for most people in the Royal Mint, this was the first time they had seen a coin produced featuring a King.

A unique difference on the coin is the absence of a crown. King Charles appears without a crown, which is tradition.

Queen Elizabeth also first appeared without a crown when her effigy was introduced, Assistant Treasurer Andrew Leigh said.

The Royal Mint expects the King Charles dollar coin to be in circulation by Christmas, with the remaining coins to be released progressively in 2024.

Queen Elizabeth's effigy will continue to circulate in tills and donation boxes for a while.

Chief executive of the Royal Australian Mint Leigh Gordon said coins have a life of 30 years.

"You can still find a 1966 coin occasionally in your change and you know based on that, we could be seeing the Queen Elizabeth coins for the next 40 or 50 years," he said.

Primary school children from Perth were also in attendance. The students disproved the expectation that younger generations might be uninterested in cash. When reporters asked if any of them still carried spare change, they all raised their hands.

Mr Leigh said many Australians were still using cash. He expected it to remain that way, along with other traditions.

"We're always going to continue to have a sovereign on the coin," he said.

The discontinuation of the 5-cent coin was also up for questioning. Mr Leigh said removing the 5-cent piece would create a rounding problem for businesses.

Other denominations with His Majesty's image will be released over the course of 2024.

First collector and investment coins with the King's effigy will be sold early next year.

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Mr Gordon said people's curiosity over coins featuring the King had peaked since the Queen's passing.

"As Australia's circulating coin manufacturer, we appreciate the importance of the transition, and we are applying our considerable skill and expertise producing Australia's coins bearing the new royal effigy," Mr Gordon said.

"The staff at the mint have been very deliberate and measured in the steps to date, and we are now well positioned to expand into production."