If you look at the wheels themselves, the right side should be a cast center wheel about 1-1/2" thick while the left is a pressed type disc balancing out the weight between sides I'm assuming for an average operators weight on level ground. And depends on what the PO mostly used it for. For instance, if they needed a little more weight on the left side for pulling a moldboard plow to keep from spinning, they may have moved the cast center to the left for that reason.