re-reading this thread, a few thoughts occur to me:
the original Holey Dollar of 1813 was struck from a Spanish Dollar (a.k.a. Piece of Eight; or Eight Reales).
The "Dump" struck out of the dollar was valued at a quarter of a dollar, and the remaining annulus was given a value, by law, in NSW, of one dollar, even although a big chunk of it was separated. Back then, a dollar was equivalent to five shillings, so the dump was 15 pence.
When the NCLT "tributes" appeared, they had to be denominated. The annulus was given a value of one modern Australian (post-1966) dollar. And the Dump, being one-quarter, was 25 cents. Which is all very neat, but as I'm not a fan of NCLT, I won't go on about it.
The sixty-cent coin mentioned above: I expect that that will be NCLT only; and I assumed that it was denominated as sixty, because this is the 60th Anniversary of the accession of H.M. Queen Elizabeth.
In 1935, the Bank of Canada issued a commemorative $25-note, to mark the Silver Jubilee of King George V. The Canadian system has $20 and $50, but not usually a $25.