These are the cast iron 72 pound starter weights for the JD garden tractors
They set deep in the wheel and then allow you to add 55# weights which I’ve got some of those too
I’ve also got some that are 35# which are smaller diameter and fit inside the wheel like the starters do
The original design on the model 400 did not need the relief cut for the axle nut but I have cut these on my lathe so they will fit the newer model garden tractors like the 318 or 430 and 455.
They also fit all the X400 X500 and X700 series tractors and the 1025R and 2305 sub compacts
They’re down at my farm south of the city.