Metal: Nickel plated steel
Weight: 5 g
Diameter: 24.75 mm
Thickness: 1.7 mm
Engravers: Ian Rank-Broadley (Obverse); George James Berry (Reverse)
On 31 July 2006, as part of a revision of New Zealand's coinage, the fifty cent was made smaller, lighter and of a cheaper alloy (nickel-plated steel). On 1 November of that year the previous larger fifty cent coin was demonetized.
Both the larger and smaller coin featured on its reverse the HMS Endeavour on which Captain Cook became the first Briton to reach New Zealand, in October 1769. The obverse, as per all New Zealand coins, features the reigning monarch, which throughout the coin's mintage has only been Queen Elizabeth II.
Click here to see the old, large-size 50c coin of New Zealand.
Source: wikipedia, en.numista.com