That is a very good question. Just like you, I am very familiar with the ones on the left since I own about 7 or 8 pair of them. I have not seen the other style previously. Keep in mind that the 15 and 16 inch rims used by Case had the common 6 on 6 bolt pattern for agricultural rims. Tractor companies don't make rims. They buy rims from companies that do nothing but make rims. Therefore, almost every brand of tractor out there had wheel weights cast for them, either in their own foundry or by a sub-contractor. I suspect that these are not Case weights but if they work.... they work. For a show tractor, I agree it would matter.