The first denomination in the commemorative "In come the dollars in come the cents" series to be in people's pockets will be the 50¢ piece.

Royal Australian Mint chief executive Ross MacDiarmid explained the new-look series feature both a shrunken queen as well as images of old shillings, half pennies, sixpence and threepence.

"It's a design where the old meets the new if you like," Mr MacDiarmid said.

"The new 50¢ pieces will go out on Monday and progressively throughout the year we will release the dollar, two dollar, twenty, tens and fives."

The freshly minted 50¢ pieces features the ram from the former Australian shilling, marking 50 years since the transition to decimal currency.

As the peak of the week's heat hit on Saturday, Canberrans arrived in droves to the commemorative open day.

It was a rare chance to start the weekend surrounded in cash, dance with Mr Minty the mint's $1 mascot, enjoy face painting or have a go on the jumping castle.

Hundreds lined up to walk through the mint factory floor to see coin designers at work and see how the mint operates in staged rooms for tool design, blank preparation, proofing and packing.

But the longest line was for the coin swap where people were eager to trade in old for new and take home some of the first new 50¢ pieces.

Branko Acimovic, from Lyneham, has collected coins for more than 30 years.

The 46-year-old said his partner often joked they'd both fall through the floor of their home due to the growing weight of his collection.

"At the moment I collect just Australian coins, but before that I collected all world coins," he said.

"It's a great time for collectors with this new release. I bought the special release 2016 un-circulated round 50¢ piece as well as a $10 with 20 of the new design 50¢ coins."

Mr MacDiarmid said the shift to decimal currency was hugely significant for Australia and gave rise to discussions about currency.

His two cents on the fate of the 5¢ coin was that it was here to stay for now.

"There was an economic argument 12 months ago that the 5¢ piece was taking 7¢ to make but that's no longer the case with the fall in copper and nickel," he said.

"The demand for 5¢ pieces has fallen by nearly half over the past three years. The question we are looking at now is what is the utility."