Just been on ebay Germany and I saw a collection of 1/2 proofs for sale with some certificate numbers higher than the declared mintage shown on perth mints own site. For example http://www.ebay.de/itm/1-2-Oz-Silbe...73696?pt=Münzen_Medaillen&hash=item27d7b4c820 According to perth mint declared mintage is 396
What's happening there is that the PM could have minted 500 coins along with 500 COA's. They will then distribute them in no particular order so some company may be sent coins with COA# 490 through to COA# 500. Whatever isn't sold is taken back and melted dow. The number of coins sold after a certain amount of time then becomes the declared mintage number. So if 379 coins are sold the declared mintage is 379 but the aforementioned dealer will have his 10 but with the highest numbered COA's. Sure the PM wouldn't remint anything without making it public knowledge first... Ahem.
In addition to House's excellent comment. The mintage for those coins has been "declared" so there will be no restriking of the coins. http://www.perthmint.com.au//documents/2010_Perth_Mint_Numismatic_Coins_311212_250313.pdf Perth's Mintage Policy http://www.perthmint.com.au/mintage_policy.aspx
