Using old 40′ box cars in woodchip service is nothing new to railways or to CP in particular. Canadian Pacific began removing the roofs of ancient 42000-series wood, double-door boxcars in the late 1960s and using these cars in Eastern Region woodchip service. They also made similar modifications to about 50 International of Maine PS-1 40′ boxcars for use in Northern Maine in a joint service with the BAR. CP never bothered to renumber these cars, but just added footnotes to the equipment register. In the summer of 1978 CP began to modify a number of 40′ boxcars for Northern Ontario woodchip service, finally giving them new road numbers in the 31200 series. This series was quite a mixed bag of cars from various series of 40′ cars, and even some of the old International of Maine rebuilds with the extended sides were also renumbered into this series and ended up in Northern Ontario service.