Wagon is an open wagon (we don't say Gondola here).
If I'm not mistaken the wagon is an ex-South Australian Railways (SAR) AOOX wagon that then passed into the ownership of Australian National (federal government, hence the green and gold livery it still wears) then recoded to RKWF/Y when AN Became National Rail and still carries the code in Pacific National (private operator) Service.
The doors have been cut off to lower the tare weight and to allow the cranes access to remove the steel products that these wagons normally carry. Mostly slab steel but you also get beams and coils. I regularly see them at South Dynon in Melbourne where the slab steel is transshipped from standard gauge to broad gauge wagons for the trip to the Bluescope steel rolling mill in Hastings, Victoria.
if I can find a decent info page I'll post them up, unfortunately outside of the Victorian Railways/ V/line very few enthusiasts have taken the time to put together comprehensive websites detailing the wagons types.
actually try here
http://www.railpage.com.au/f-p1301472.htm
