Where have all the old coins gone?

If you're no penny-pincher, it's probably your loss.

The Reserve Bank is expecting to receive just one-third of the outdated 50c, 20c, 10c, and 5c coins by the time their expiry date as legal tender rolls around on November 1.

This week about 85 million new coins, with a value of $15 million, were distributed to hundreds of retail bank branches up and down New Zealand.

That might seem like a hefty number, but considering the number of coins already in circulation, it's a small drop in the piggy bank.

Since decimal currency was introduced in 1967, the Reserve Bank has released 1 billion coins of varying values into the New Zealand economy.

The manager of the new coins project, Alan Boaden, said the bank expected only 300 million old coins to be redeemed over the next few months.

"A lot of them, particularly the 5c coins, get lost very easily. Tourists also take them out of the country. Many coins will be continue to be held in jars and drawers.

"Businesses that have large stocks of coins, such as buses, taxis, and vending machines will hold many old ones," Mr Boaden said.

"We expect to issue more as the year goes on."

The Reserve Bank purchased 230 million new coins from the Bank of Canada - enough, it says, to last for about the next 36 months.

When new euro currency was introduced in Europe, it took little more than a month before 90 per cent penetration of the new coins was achieved. A similar result was expected in New Zealand.

No negative feedback or complaints had been received by the Reserve Bank from retail banks about the new coins, he said.

Tolerances over the weight of the new coins were tightly regulated. "All have been checked by the Canadian mint, both for their physical properties and their electronic signatures," Mr Boaden said.

Electro-magnetic signatures were a feature of the coins and acted as a safeguard against counterfeiting.

Modern vending machines and parking meters had the ability to check the authenticity of the coins using the new technology.

Although the question of replacing the $5 note with a coin was considered by the bank, Mr Boaden said there were no plans to do so "at the moment".