The interwar period was a strange time for technological development. What we have here is an air cooled 9-cylinder radial engine was for use in an M4 Sherman according to the owner. While searching for suitable engines for armored vehicles in the 1930s these radials were found to be the only thing powerful enough and were found many of the US army’s homegrown armor up to and including WW2. These radials would eventually be replaced by a Ford developed V8 later on in the war.
I’ve known about the radial tank engines for awhile but have never seen one in person before. Pretty cool.