Australian Coin Collecting Blog - Ex Noble Sale 83, Lot 66 (2006) a dodecagonal 1969 50 cent coin struck with two obverse (Machin QE2 portrait) dies in regular medal alignment. It is unusual that it is struck without a 180 degree rotation as double obverse or reverse error coins are always struck in coin alignment if genuine. The coin is about 0.8 of a millimeter over size measuring 32.3mm from flat to flat. The coin weighs 14.6 grams which is almost a full gram under specification. It is suggested that the coin be tested on an XRF to determine if it is an underweight copper nickel planchet or a different material. Examination of both sides of the coin shows extensive fish-tailing suggesting the entire coin was struck out of collar. Metal flow lines are visible on both sides of the coin so we are confident it was struck and not cast.
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