Carn't stop myself.

[Mike Cecil]

510 unit sign was 26 Transport Squadron, serving as part of Field Force Command late 70s/early 80s.

The 6841 is the Unit Serial Code for that unit. The painted 'tree' under it represents the colour code for each numeral:
6 =Buff
8 = brunswick green
4 =grass green
1 = signal red

The 'roo and ARMY were supposed to be painted in orange.

Only units that were intended for operational deployment were supposed to carry the Unit Recognition Mark, as detailed in the Quadripartite Standardization Agreement 1079 - Common Vehicle Marking and Identification.

The 12 is the bridge sign.

Nice truck.

Mike