WO type iron ore waggon WO 31204 is one of a batch of eighty six built by WAGR Midland Workshops between 1967 and March 1968 with fleet number 101 for Koolyanobbing iron ore operations with a 75 ton and 1018 ft.³ capacity, Binduli Triangle 22nd August 2010. This unit was converted to WOS superphosphate in the late 1980s till 1994 when it was re-classed back to WO.