My training and understanding is that a pack is a group of wagons permanently joined together by a solid draw gear or sharing a common bogie. A Unit is a group of wagons that are assembled together for ease of maintenance and inspections.
.... but that is getting away from the topic.
When Australian National introduced the first articulated and permanently coupled container wagons in the late 80's they used the term pack for wagons sharing a common bogie and unit for fixed draw bar coupled wagons. My understanding National Rail continued to use this same terminology for their container wagons.
I am not sure when fixed draw bar coupled hoppers were introduced to NSW but I assume this was when Freightcorp was around and they could well have used a different terminology for this type of wagon to AN and the different terminology has continued to be used by the NSW coal operators.
It may have been a fair while back but I'm pretty sure I've seen batwing sized hoppers on Stratford coal trains .
While they may not strictly be Batwing types, the current Bradken design NHYH, NHEH and NHIH types are also produced in a reduced height version that carries 100t fully loaded, used by Centennial (PHTH) and Gloucester Coal (PHGH).
I assume the Gloucester Coal wagons are used on the North Coast.
The NHCH code that I mentioned is indeed an ECP wagon but used by PN Queensland. I apologise for including it in the Hunter listing.
The NHCHs are the aluminium trial wagon pair used for comparison with the NHGHs.
They were mainly compared with the Bradken NHAH wagons....
When the NHGHs arrived, the NHCHs seemed to be out of service. I did get a photo of both pairs numbered 0011/0012 at Gladstone.
They are really composite steel and aluminium, they have steel centre sills.
Are the 120T gross hoppers from Stratford fully loaded ? If so that's 30 TAL on the lower NCR .