As a collector of error coins in particular errors of Australian coins there’s one type of error that constantly eludes me. This article features 2 different, but very similar New Zealand 50c coins of this error type.
This coin error is called a split planchet error and there are a few types of this particular error. Split planchet means the coin blank has split, in this case in two separate pieces. The coin planchet splits (often) due to a metal impurity and this split can occur before the coin is struck or after. It can present itself as a complete split or an incomplete split known as a clamshell. You could have a struck coin which then splits into two pieces or (in the case of these 2 different New Zealand 50c pieces) the planchet split and the coin was then struck post-split on an underweight planchet.
You’ll see in the images, the reverse of the top coin is struck over the split surface still showing those tell-tale metal striations. The bottom coin shows the split surface as the obverse. The design is weakly struck equally on both sides of the coin with weakness more obvious nearer the legends and rim, a tell-tale sign of a coin struck on a planchet severely underweight.
The most interesting thing about these 2 coins is that they are eerily close to being the same coin planchet, fallen in half and then struck as two individual coins. They are both of the same country, denomination, design and effigy. Sadly though once weighed, they are heavier than a complete 50c so they are from two different split planchets.
I’m very pleased to have these two coins in my collection as it’s Australian cousin is very hard to come by indeed, We’ve only seen two examples in the past 10 years of an Australian coin struck post-split.