Hi, by the sounds of it, your boy is a standardbred (a trotter or pacer),the brand you describe is called a freeze brand and would be under his mane yes?. I will go google standardbred australia and see what happens , never looked up a trotters brand before, but done plenty of racehorses

Australian Harness Racing
Go to search, and select horse search (HRA online)
Select freezebrand and that will tell you how to read it.
Goodluck and let me know if you cant make sense of it.