Fascinating Phenomenon With Some 2012 5-P Coins !

It seems to me far more likely to find actual proof coins in circulation, rather than some mixup (erroneous or deliberate) in dies at the mint. I'm not quite sure how The Royal Mint does things, but I'm pretty sure that at the Royal Australian Mint, proof dies and uncirculated dies can't simply be interchanged; the presses they fit into are different. A proof die fitted into the circulation press would be like a square peg in a round hole.

That being said, I don't think the coins you're finding are actual proofs. The "frosting" effect on proofs covers the entire portrait; your "frosting" appears only on the high points, with the low points (such as deep in the queen's neck) showing mirror finish. I can't think of any process that would make the frosting selectively "go away" like that.

These 2012 coins are made of nickel-plated steel, rather than the traditional cupronickel used for pre-2012 coins. They will wear differently. Specifically, I think what you're seeing is the highly mirrored nickel plating wearing off the high points, showing either bare steel or an unpolished plating material underneath (again, I'm not familiar enough with the method of production of the blanks to say for sure). I suspect you aren't seeing it on newer coins either because they've changed their plating technique to avoid this problem or that the newer coins simply haven't been in circulation long enough for the plating to wear down to that point yet.

Here's 3 I found in what was left of my steel 5p's.



The middle and right ones, I assume, are due to circulation.
The left one certainly seems different.
However, as the next pic shows, there's a frosted area behind the D.G. too :-/




-------------

Has anyone heard anything, or even noticed infact, that there appears to be some wired edge 1992 5p's in circulation. (Just like the 10p's)
Weight and thickness are the same.

While thinking about this subject an interesting idea just hit me , given that the coins in question exhibit partial frosting - I thought, what if the coins were meant to be proofs but the failed quality control checks due to lack of full frosting effect (possibly due to some imperfection in the die) hence some clever lady or chap at the mint thought it would be best to just toss them into circulation instead of binning them since they are with all intents and pruposes 5p`s