The new New Zealand coins will be released into circulation on the 31st of July.There will be a 3 month transitional period in which both old & new coins will continue to circulate,after which the old coins will no longer be legal tender.The 5c. coin will no longer be struck.The 10c. coin will be a copper-coloured coin.The 20c. & 50c. will be a lot smaller in size & will be struck in a different metallic composition at the Royal Canadian Mint's branch in Winnipeg.
Here's a link; http://www.newcoins.govt.nz .
Aidan.