Tractor - agricultural, wheeled - International Harvester Co. 10/20 c. 1925. by International Harvester Corporation Chicago, Illinois, United States of America, circa 1925. In 1921 IHC introduced the next generation of their lightweight designs with the 15/30, and by 1923 they had introduced a smaller version, the 10/20. Both tractors shared some novel features. IHC had adopted Fordson's cast unit construction, but had modified the idea by providing a cast iron hull forward of the gearbox in which the engine sat separately, unlike the Fordson where the engine was an integral part of the tractor's structure. This did offer certain benefits when it came to maintenance. Another feature was that both were marketed as 'Triple Power' Tractors; beside the usual power 'outputs' of the drawbar and the belt pulley IHC provided an optional power takeoff which could easily be fitted to become integral with the tractor. The power take off (PTO) was a shaft drive which could be used to power trailed implements such a