Above is a 1954 Fordson tractor with square back wheels. Actually, the top and bottom flat part is composed of two hinged plates and sometimes it is an hexagon as it turns. At the 1:33 mark they have good slow motion sequence that shows the wheel mechanism in operation.
This setup was designed to dig trenches for drainage pipes in wet, soggy soil. It isn't the only odd wheel assembly to get bolted onto a Fordson tractor -- earlier I've posted about the Fordson Snow Devil.