From Wikipedia article, (complete)(Links and Cats redefined for tractor wiki)(Could be extended by adding Model listing and info below by anyone with knowledge of these engines) Petters Limited (known as JB Petter & Sons of Yeovil until 1910), were a maker of stationary petrol and diesel engines from 1896 onwards. In 1915 Petter founded Westland Aircraft Works (renamed "Westland Aircraft" in 1935). In 1986 Petters Limited merged with one-time rivals companies RA Lister & Company to form Lister Petter.