Wisconsin AC4 - 1946 - 16 BHP @ 2600 RPM - A 4 cylinder air-cooled engine with a rope start!!

They were commonly used in generator sets and balers. This engine has a pretty serious looking belt pulley on it and so presumably was used on a baler or similar.

This engine was made by Wisconsin in America but these were also made under licence by Lister between 1930 and 1938. Lister named it the ACL4. These engines seem to be fairly rare in the UK, even the Lister manufactured versions are uncommon.