I was looking at legislation about coins in Australia and noticed that the $5 coin is missing from the Schedule—Standard compositions of coins. https://www.legislation.gov.au/Details/C2007C00565 Does this mean that the coin can be made out of whatever the Treasurer wants?
At a guess, I would say that is due to the $5. coins being NCLT only. But don't think they are 'valuable' …. A 1988 'Parliament House' commemorative $5. coin can be easily acquired for just $6.