Jeff, do I read that as the fact that you have a S2 as well as a S2a Wksp. (I won't let anyone else know
)
The diamond marking is used by a number of Corps to denote which Squadron, battery, Company it belonged to besides Armour. (Don't tell the tankies this though, as they think they are the only ones there!)
Without any other signage we are none the wiser as to who it would have belonged to. We need a Tac sign or some such thing.
As for the 2 W 3 on the workshop, the "W" denotes "workshops" and the number 3 denotes the third vehicle in the particular unit, (1 being the OC, 2 the 2i/c and then in the case of RAEME (who operated a number of specialised vehicles) other numbers denoted particular pieces of plant within the Unit.
In many cases (especially Transport) the unit identification would also have been displayed on the diffs for night-time convoy recognition. I say this because I suspect that your vehicle either belonged to a Div Wksps or at least a Transport Unit LAD.
As for the "2" that could be interpreted differently depending on the parent Corps, but generally denotes the Platoon/squadron or parent unit.
When you get a chance have a look here, there is some rough basic info on these pages.
http://www.remlr.com/index_restore_info.html then go to "Australian Army Vehicle Markings".
Regards
Glen