The older ones are harder to find in a wider width that will cover the tracks of your tires of a larger loader ike a 843.
Also most are chain drive, which s ok but you have a chain to maintain and a oil compartment to make sure is not leaking.
Newer tillers have direct drive drive and some ike the Erskine ones have a drive motor on each end for more torque on the rotor.
I'd say a get good look at the tines for wear and see if any are missing. If it has a chain, sampe the oi for wear and steel. Try to move the rotor shaft up and doen to see if the bearings are still tight.
Ken