the 1925 Ford 5/8 size tractor Henry Ford had built for his grandchildren on a Model T frame

In 1925, Henry Ford asked his special projects design engineer, Howard Simpson, to design a miniature tractor for his grandchildren. At the Henry Ford Estate named Fair Lane in Dearborn, Michigan, along the Rouge River, Ford and his wife Clara had built to scale a small working farm for the grandchildren and requested of Simpson that the tractor be approximately 5/8 scale to accommodate a 10-to-12-year-old boy to drive. Once completed, it became part of the reduced size set of farm equipment for the grandchildren and was also displayed at fairs.

"When we first started this tractor, we found a governor on the fuel line to control how fast it could go, and a lock on the ignition to keep children from starting it without permission," says Aumann. Adding to the uniqueness of this tractor, the name on the front of the radiator says 'Fordsons' instead of the standard 'Fordson.'

https://www.prnewswire.com/news-releases/tractor-custom-built-for-henry-fords-grandchildren-offered-at-public-auction-300825785.html