Ah, I had a look to see what the 2/6th Armoured Regt Stuarts at Buna had as markings; it was an armoured arm holding a battleaxe (white on black), but the unit patch was the WW1 tank badge as above, but on a diagonally-split red/green backing. From further reading, it seems that the div sign was the arm with battleaxe, but the individual regiments wore the WW1 tank badge with different coloured backings.