WO type iron ore waggon WO 31281 is one of a batch of eighty six built by WAGR Midland Workshops between 1967 and March 1968 with fleet number 161 for Koolyanobbing iron ore operations, with a 75 ton and 1018 ft³ capacity, on empty train 1416 at Hampton, 22nd August 2010. This unit was converted to WOC for coal in 1986 till 1994 when it was re-classed back to WO.