World market in Australia.
A reputable coin dealer in your area may be able to assist, alternatively, you could try eBay.
This coin is so completely absent from any Australian coin catalogue that I am suspecting it is not an Australian coin. Some countries mint coins celebrating international historical events. If there is anybody claiming to have one of these coins, please provide some detail like a country of issue, denomination, what the coin is made from, year of issue, etc. On the assumption that this is a collector coin, all the necessary information should be on the packaging.
Any genuine coin with a genuine flaw would be worth something more than usual. The Australian 1966 10 cent coin has no documented occurence of any minting flaws. A reputable coin dealer should be able to give a valuation.
The Australian Two Dollar coin is made from copper, aluminium and nickel and is of a gold appearance. Very occasionally, some Proof coins are made from silver and issued in sets. The 2000 $2 coin was not one of these. If you have a silver $2 coin, it has been plated. Modified coins are worthless as a collectible.
The Australian Dollar coin was first issued in 1984. There was a One Dollar coin minted in 1967, but it was not for general circulation, and it is not even regarded as an official Australian coin. It was known as the "Swan Dollar". It was a very limited mintage, Proof coins in silver and gold specifically for collectors. The obverse depicts a swan in flight, the with the word "AUSTRALIA", a crown and 1967. The reverse has a design of Australian flora with a large 1.00 across the coin. In their original condition and packaging, the silver coins could get up to $1,000 AUD. The gold coins could get up to $12,000 AUD. Only ten were minted and two are known to have been destroyed in the Ash Wednesday bushfires.
It is extremely unlikely that a 2000 general circulation coin would be minted in 2001. It is not so unlikely that some bullion Proof coins might be minted in the year after the date indicated on the coin.
It is extremely unlikely that an Australian decimal coin with minting errors survived the inspection process and went into general circulation. The closest acknowledgement of an error on an Australian 2 cent coin is that in 1967, 1968 and 1981, the designers initials were left off the reverse of the coin. If it turns out that you do have an Australian coin with a genuine minting error, take it to a reputable coin dealer for a valuation.
Is there some sort of coin shop in your area? They may buy it.
There have been dozens of Australian coins issued for various Olympic games over the years, some silver, some of silver appearance. Please narrow down the possibilities with a year, a denomination and a design feature.
One can sell their gold in a number of different ways. Some of the best ways to sell gold are to pawn shops, jewelers, coin shops, or cash for gold businesses.
Coin shops, pawn shops, some jewelry stores.
No general circulation Australian decimal coin could be considered to be valuable. Any 1981 coin in absolute pristine mint condition might get $2 to $4, otherwise, they are worth face value. There is one variation, the 1981 20 cent coin minted at the Royal Canadian Mint Winipeg, shows the platypus with three and a half claws. These may have some collector value.
Who knows. If all of a sudden, for some bizarre reason, every coin collector in the world wanted a 1943 Australian Penny, it could be worth $1,000 or more tomorrow.