There are 2 states of Die I. Die I White Wattles, and Die I. The White Wattles as has been mentioned was caused by the use of unsatisfactory ink in the first printing.
With the White Wattles, the T and A are pronouncedly joined, not just joined. The King's ear is mostly unshaded. But the real tip with the White Wattles that hasn't been mentioned is that there are two frame breaks on the inner left frame - one about level with the epaulette on the King's shoulder and one between the lower lip and chin.
Here is an image of a White Wattles (borrowed from another site - I disposed of a lot of my Aussie collection to concentrate on Victoria.

)

You can see the 2 frame breaks on the inner left frame - look about 6 lines up from the left numeral 3, and up again for the next one.
Die I is the same die, just better ink. This cleared up the wattles, the King's ear is better but the chin still undefined. The T & A are joined to a lesser extent.
Retouching the copper plates led to Die Ia. The T & A are separated - the T tapers at the lower end - on the same angle as the slope of the A.
Die II was a re-cutting of Die I on a new transfer of the original die. POSTAGE was re-engraved to appear even and the King's chin was strengthened by a continuous line.
Die III was a completely new die. It's identified by the longer epaulette at right.
Hope this helps!
Balf