In 1966 Australian five cent pieces were minted at both the Royal Mint in London and the Royal Australian Mint in Canberra. Those struck by the Royal Mint carried the standard design while those struck in Canberra have a shortened spine. In the image below, the coin on the left is a Canberra five cent and the one on the right a London.

I've always found this difference difficult to spot. The shortened spine is the one immediately below the two that cross over, and the Canberra is missing the tip of the spine giving it a "stubby" look. From 1967 onwards, the five cent minted in Canberra all have the standard design.