I saw a post about rare 20 cent coins so I went through my change looking for will and kate. Found 0. Then I saw info about the wavy 20 cent. Went through my change and found this. Source: Value? Pretty dinged up
You went looking for will and Kate and found this! I would swap you a mint roll of will and Kate's 20c coins in a heart beat! The wavy is a far better score congrats however are you able to take a vertical picture of the wave section close up?
On page 125 of the 2013 Pocket Guide To Australian Coins and Banknotes - By Greg McDonald. 1966 Reverse Die Variety - "Wavy Line" Baseline. Raised section on top of the horizontal bar on base of "2". Struck at the Royal Mint, U.K. A normal version is worth around $1200 in Extra Fine grade; $2500 in Uncirculated condition and $3950 in Choice Uncirculated.
This is the best I can do with my phone. In my change I only had 2 1966 coins. Lucky I got it. Source: