WO type iron ore waggon WO 31299 is one of a batch of fifteen built by WAGR Midland Workshops between July and October 1968 with fleet number 178 for Koolyanobbing iron ore operations, with a 75 ton and 1018 ft³ capacity, loaded with fines at Bonnie Vale, 28th May 2005. This unit was converted to WOS superphosphate in the late 1980s till 1994 when it was re-classed back to WO.