If Australia's longest-serving prime minister Sir Robert Menzies had had his way, this weekend would mark the 50th anniversary of the introduction of the royal.

It was the name Menzies — a staunch supporter of the British monarchy — wanted for the new decimal currency that was introduced on February 14, 1966 to replace the imperial system of pounds, shillings and pence.

Loading...

Peter Rees, author of a new book Inside The Vault: The History And Art Of Australian Coinage, said Menzies' preference sparked outrage and "a national backlash".

"Government MPs around the country were just being inundated with people who said, 'this can't be accepted into our currency, we're not going to trade in royals'," Mr Rees said.

The government eventually decided the new unit would be called the dollar, and over the next three years Australians were bombarded with an advertising campaign to prepare them for the changeover.

It included a televised jingle to the tune of Click Go The Shears by a character called Dollar Bill who sung:

"In come the dollars, in come the cents, to replace the pounds and the shillings and the pence."

The huge task of supplying banks for what was known as C-Day (Currency Day) required what Mr Rees described as "the greatest movement of money in our history".

"Convoys of semi-trailers under armed guard criss-crossed the nation; it even had its own name — Operation Fastbuck," Mr Rees said.

"After 50 years we may take the changeover for granted, but this was a reform that affected everyone."

Mr Rees said one of the unknown stories he uncovered while researching his book was the tension in a competition to design the new coins created.

According to Mr Rees, it "pitted together" six Australian designers.

"Fortunately we ended up with Stuart Devlin's designs [of native fauna] which have stood the test of time," he said.

Stuart Devlin's proposed coin designs included a cockatoo and a marlin. ( Supplied: Royal Australian Mint )

To mark the 50th anniversary of the currency changeover, the Royal Australian Mint is holding an open day this Saturday.

The public will be allowed onto the factory floor for a rare, close-up view of how coins are made.

The mint is also releasing a new series of circulating coins that will feature pre-decimal designs from the half-penny to the florin underneath a smaller effigy of Queen Elizabeth II.

The mint has produced nearly 15 billion coins since it began operation in February 1965.

Chief executive Ross McDiarmid said it faced the challenge of keeping coins relevant.

"Clearly with the disruption of new technology there's a risk that coins may lose their utility over the next 20 or 30 years or so," he said.

"In Europe, for example, they've seen a 5 per cent increase in demand for circulating coin but in Australia we've seen a decline."