The Reserve Bank of New Zealand does not issue all coins in all years. The RBNZ only issues sufficient coins to keep the number of coins in circulation at what it perceives to be the required quantities.
Since the old 10, 20 and 50 cent coins were withdrawn in 2006, the issue of new coins since then is as follows -
10 cent coins - 205,600,000 total issued
20 cent coins - 196,600,000 total issued
50 cent coins - 90,200,000 total issued
All issues of the 1 and 2 Dollar coins are potentially still in circulation. The issue of 1 and 2 Dollar coins since 1990 is as follows -
1 Dollar coins - 92,700,000 total issued
2 Dollar coins - 88,050,000 total issued
Damaged and worn coins are withdrawn from circulation as they are returned to the bank.
The 10 and 20 cent coins are relatively recently issued, so not many would have been withdrawn yet.
According to the RBNZ figures, it would seem that the 10 cent coin is the most used closely followed by the 20 cent coin.
As of my last update, the most wanted coin in New Zealand is often considered to be the rare 1935 New Zealand Crown, which is highly sought after by collectors due to its historical significance and limited mintage. Additionally, the 1967 New Zealand 50-cent coin, featuring the Kiwi bird, is also popular among collectors. Interest in specific coins can fluctuate based on market trends and collector enthusiasm. Always check with local numismatic resources for the latest information on sought-after coins.
The highest denomination New Zealand coin in general circulation is the Two Dollar coin. The highest denomination coins minted for the Reserve Bank of New Zealand are the 1990 gold $150 coin, and the 1998 platinum $150 coin.
The kiwi, a bird native to New Zealand is probably the bird most associated with the country. It appears on a New Zealand coin, there is a fruit called a kiwifruit, it is the name of a rugby team, and pakeha people living in New Zealand call themselves 'kiwis' just as often as they call themselves 'New Zealanders'.
You will find most the answers to New Zealand coin questions already on WikiAnswers if you use the format - What is the value of a 1954 New Zealand Halfpenny etc.
From 1967 to 1989, the Kiwi was featured on the reverse of the New Zealand 20 cent coin. In 1990, a commemorative 20 cent coin was issued featuring the ship HMS Tory. From 1990 to present, a Hei Tiki Maori carving is featured on the reverse of the New Zealand 20 cent coin.
The New Zealand Halfcrown was issued in most years from 1933 to 1965. Any collector value would depend on the year and condition of the coin.
Most New Zealand silver Proof coins are sterling silver containing 92.5% silver.
The large non-circulating New Zealand One Dollar coins have been minted in most years since 1967 as a cupro-nickel coin for the collector market. In most years they were minted since 1974, they were also minted as sterling silver (92.5% silver) coin. Proof coins are sold in a protective packaging which should indicate what the coin is made from, particularly if it is made from a precious metal. The 1977 New Zealand large One Dollar coin (Waitangi Day) was minted in both cupro-nickel and sterling silver.
The New Zealand Florin (Two Shillings) was first issued in 1933 and last issued in 1965. The most valuable New Zealand Florin would be 1936 coin. A distant second would be the 1940 and 1946 coins. The 1946 coin with the value shows the kiwi with a flattened back. It should be noted that the valuable coins only have the high value if the coins are in "mint uncirculated" condition.
A jitney, as used in your question, is an old term used when referring to a nickel coin. It is not in use very much today.
The value of any coin would depend on the year and the condition. Most New Zealand decimal coins, unless they are in mint uncirculated condition, would be worth face value only. NOTE - All New Zealand pre-2006 50 cent coins are no longer legal tender, but they are redeemable for face value at the Reserve Bank of New Zealand.
The New Zealand 5 cent coin was withdrawn from circulation in 2006 and is no longer legal tender, although they are redeemable for face value at the Reserve Bank of New Zealand. There were two variants of the 1967 New Zealand 5 cent coin, one with the sea in the background and one without. The coin without the sea in the background might fetch up to $100 NZD if it is an absolute mint condition. The 1971 5 cent coin might fetch up to $20 NZD if it is an absolute mint condition. The 2004 5 cent coin of which there were only 48,000 issued, might fetch up to $135 NZD if it is an absolute mint condition.