In 1981 Australian five cent pieces were minted at the Royal Australian Mint in Canberra, the Royal Mint in Llantrisant, Wales and the Royal Canadian Mint in Winnipeg. The Royal Mint five cent cannot be distinguised from the RAM issue, but, similarly to the better known 1981 twenty cent, the Canadian coins show some differences from those struck at the other two mints. In the image below, the coin on the left is a Winnipeg five cent and the one on the right was minted in Canberra.

The obverse of the Canadian five cent has flat fields whereas the field of the issues from the other two mints is concave. But the easiest way to spot the difference is to examine the details in Her Majesty's hair. The closeup below clearly shows the difference.

Winnipeg                                Canberra

Similarly to the 20c, the Winnipeg 5c is common in low grade but since it was not hoarded at time of manufacture, it is very scarce uncirculated or better and as an easily detectable variety is undervalued in the catalogues.