If you look at the Platypus' hand under the '2', one of the claws on the 3 1/2 claw coin is half the length. This indicates that the coin was struck in Canada as opposed to the Wales or Canberra mints.
The easiest way to tell the difference is the 3 1/2 claw as they call it has a flat field. That is the area around the Queen is flat as opposed to concaved. The bottom of the letters are scalloped vs straight as on the common one (4 claw).
