New Zealand Mint is due to sign a $5 million, five-year deal with the Premier of Niue tomorrow to extend its exclusive rights to use the Niuean effigy on its collectors' coins.

The deal means the Auckland-based business can use the Queen's head with "Niue" on the back of its coins, meaning they are legal tender in the tiny Pacific nation.

But because their face value may only be $2 or $10, the coins are worth much more as precious metal or to a collector, who pays around $200 for them.

"We don't produce their currency for general circulation," a NZ Mint spokesman said. "This is really about the collectors and the numismatic market."

The mint also deals in investment gold coins but a fifth of its revenue now stems from making and selling coins for the billion-dollar global coin collectors market.

Investment coins did not need an effigy, the spokesman said.

"Anything without an effigy is a medallion - the gold medals at the Olympics are medallions."

However, collectors did not collect medallions and coins were not coins without a government effigy, which was quite difficult to secure.

The deal was good for both parties, giving the mint continuity and a boost for the cash-strapped Niuean economy, which received a percentage of sales.

"It's quite a good relationship, really."

NZ Mint is coy about releasing its sales figures but said its coin business grew by $6m last year.

Almost all its collectable coins are exported and 60 per cent of its sales are to Russia.

As part of the deal, the company will annually sponsor two students from Niue on Outward bound scholarships.

- © Fairfax NZ News