Austraila's Round 50 cent coins

[trout]

The double bars are pretty faint though.

Virtually every 1966 50¢ I have looked at has some sign of double bars. The question is how pronounced do the bars have to be to call it a proper double bar rather than just a pretender?

Have a look at the link gnome added to his post on page 2 of this thread Jeff, The 1966 London Pattern 50c coin looks to be the real double bar.
Like you said most of the rest are pretty well "Pretenders" compared to the London coin, Including mine