Tractor pulled mowers are usually in the form of an attachment to a tractor. The 4520 was John Deere's first turbocharged tractor. The basic push mower mechanism is also used in gangs towed behind a tractor. They are unloaded using a tractor and loader or skid-steer loader. Numbers used the same system for towing vehicles on tractor plus tow over tractor rating. These silos are usually unloaded with a tractor and loader. Play Town Farm for children including tractor ride. The trenches were dug by a cable plough towed by a Caterpillar D8 tractor. T track tractor at at least three farm shows. In 1974 the 5 millionth International Harvester tractor, a 1066, was manufactured. Kaesong has factories for producing agricultural machines and tractor repair. The most common use of the term "tractor" is for the vehicles used on farms. In 1928, Henry Ford canceled U.S. production of the Fordson tractor. Its chassis was used as the base for the C7P artillery tractor. Official production of the 8N tractor began in July 1947.