The 1 1/2d KGV is probably the most studied of all Australian stamps. There are literally hundreds of known varieties that are listed in ACSC, and they have not possibly found them all. However, I think your example falls into the broad category "Tin Shed Flaws". Go ahead and search for this phrase in this forum, and you will see some discussion on it.
If you really feel adventurous, scroll through the pages in this link:
https://www.stampboards.com/viewtop...1ac95a3b1e40Look under the 1 1/2d Die 1 Brown/Green/Red and you will see links for plates 1-4, 5-6a, etc. It should keep you busy for a few days trying to find your variety.
I've actually done the same and found some items eventually. Even if you don't find it, it would probably be worth a little something extra to the specialist. Good luck.