In the world of agricultural equipment, many brands used 15" and 16" rims with the 6 on 6 bolt pattern. All of these rims came with the same pattern of 4 square holes in them for wheel weights. Therefore, almost all of the brands offered cast iron wheel weights for their machinery that also fitted wheels on competing brands. OEM Case cast iron weights scale in at 37 lbs each and look like the discus you may have thrown in track and field events. They are stackable and were sold in sets of 4 or 6 .
If the pair you got extend outside of the actual rim center, then they are not OEM Case garden tractor weights but they could be OEM Case AG Division weights meant for the front wheels of tractors or to go on combines etc.