An Australian 1954 to 1961 Ten Shilling note (Coombs/Wilson)(depending on the serial number), uncirculated and in absolute mint condition could fetch anything from $400 up to $32,500 AUD. If it has been circulated but still in good condition, it might fetch anything from $25 to $18,500 AUD.
A reputable coin dealer will be able to give a more accurate valuation.