New Zealand 2004 5 cent piece
The 2004 5c piece is one of New Zealand's rarest 5c pieces: although 15,000,000 circulating coins were struck by the Royal Mint, the imminent arrival of Smaller Change and the phasing out of the 5c piece in 2006 meant that only a tiny fraction of the mintage ended up being released into circulation - the release of the older, large and soon to be redundant 5c pieces would have been wasteful as they would need to have been recalled again within a short amount of time. By the Reserve Bank of New Zealand's estimation, only 48,000 coins ended up being released into circulation (p5, Grant, The John Bertrand New Zealand Coin and Banknote Guide, 2014). The rest were destroyed and the metal recycled.
Mint sets were also produced with 2004-dated coins. While a mintage of 3,500 was authorised, the Royal Australian Mint only struck 2,800 sets (p39, Grant, The John Bertrand New Zealand Coin and Banknote Guide, 2014). It is estimated that 1,750 proof sets were also struck with an authorised mintage of 2,000 (p45, Grant, The John Bertrand New Zealand Coin and Banknote Guide, 2014).
Unfortunately the circulation and mint set coins can be quite difficult to distinguish. The circulating coins have generally thinner lettering on the obverse legend, but the easiest distinguishing feature is the 4 in 2004: on the mint set coins the two cross bars and the sloping bar are all of roughly equal thickness, whereas on the circulating coins two cross bars are noticeably thicker than the sloping bar.