These two vehicles were built by Commonwealth Engineering Co., Rocklea in June 1957. Two of a batch of 50 (31242 - 31276) all were delivered between June and November 1957. This was the first type of all steel insulated wagon purchased by Queensland Railways. These wagons were cooled by the use of ice in the overhead hatches provided at each end of the 32ft.Oin by 7ft.6in.(9754 X 2286) body. They were both fitted with a upgraded cast steel bogie type during December 1960 and February 1961 respectively and lead similar lives until February 1972 when 31264 was fitted with mechanical refrigeration and reclassified CMR. The refrigeration system was driven by a Southern Cross 20hp diesel engine built by the Toowoomba Foundry. CMIS 31265 was finally written off in November 1981 with CMR 31264 following in March 1991. The original drawing for these vehicles was numbered 6215.