The new coin has already generated a lot of overseas interest but New Zealanders would get the first chance to purchase one, Mr Allison said.
The coin to commemorate Prince George's birth sold out within two weeks and New Zealand Post was expecting a lot of interest this time around, he said.
"There's a certain mana or status about this coin," Mr Allison said.
"There's bound to be other memorabilia out there but a coin that's officially by New Zealand has a lot of sentimental value. There's something special about Wills and Kate and the public has really connected with them."
A coin was also minted by New Zealand Post to mark the birth of Prince George in 2013, incorporating a stylised koru, which sold out quickly.
The organisation is the only official issuer of legal tender commemorative coins in New Zealand.
Delivery of the new coin is expected in July and coins are available for pre-order.
Go to nzpost.co.nz/coins for more information.