If by a "mule" coin you mean for example, a 1999 Australian 2 Dollar coin reverse struck with the obverse of a different coin, like a similar size New Zealand coin or, on an Australian 10 cent blank, this is an accident of the minting process and a valuation cannot be anticipated.
Examples of your coin have sold on eBay for up to $26 AUD.
A reputable coin dealer will be able to give a more accurate valuation based on inspection of your coin.
This "mule" coin came about when the obverse of the Indian Quarter Anna coin and the reverse of the Australian Halfpenny were used together. There is thought to be 10 or less of these coins in existence. Both the Indian coin and the Australian coin were minted at the Calcutta Mint.
The rarest Australian Halfpenny is the 1916 (mule) coin, the 1923 coin is rare, and 1915, 1918 and 1939 (kangaroo reverse) coins are considered to be scarce.
It is a mule.
Any collector value would depend on the country of origin of the coin, the denomination of the coin, the condition of the coin and how far off the mark the problem is. A "Mule" coin is where the obverse and reverse dies are not matched as per the official specifications for the coin. More frequently, it is, for example, a ten cent coin struck on a five cent blank or planchet.
If it is a proper one and not a mule it is worth £614
There is a rare type of $1 (one dollar) Australian coin dated 2000 that is worth significantly more than it's face value - it is referred to as the "Mule" dollar, as the obverse (heads) die used to strike it was designed to strike 10¢ coins only. Not all 2000-dated Australian $1 coins are like this however - the "mule" can be identified by the thicker rim around the edge of the obverse / heads side. Values for this coin range from approximately $300 right up to the thousands for one in close to mint condition.
Mule Variations was created on 1999-04-16.
by the looks of things the answer to your question is yes it would be a mule. A "Mule" is a coin whose obverse is not matched with the official reverse.
More information is needed, please be more specific and post new question.
Approximately 500 pound. Which currently is 730 US dollars or 1030 Australian Dollars. Andyclimax (Syd, AUS)
The rarest Australian Halfpenny issued for general circulation would be the 1923 Halfpenny. It is thought that there were only 15,000 minted. One of these coins, even in poor condition, might fetch over $1,000 AUD. The rarest of all Australian Halfpennies is the 1916 "mule". It has the reverse of the Australian Halfpenny and the obverse of the Indian Quarter Anna coin struck on an Australian Halfpenny blank (or planchet). These are an error coin and should never have made it into circulation. It is thought that less 10 were struck and are worth tens of thousands of Dollars AUD. All known examples of this coin are accounted for.
An Australian 1936 bronze Halfpenny (George V), uncirculated and in absolute mint condition could fetch up to $225 AUD. If it has been circulated but still in good condition, it might fetch anything from $0.75 to $22 AUD.There were 5.577 million minted.An Australian 1936 bronze Halfpenny (George V)(Proof), uncirculated and in absolute mint condition could fetch up to $35,000 AUD.A reputable coin dealer will be able to give a more accurate valuation.