I'm not buying the wheel weight idea. If you want to add weight ,you would want to use all 4 bolts ,why would they leave one out. With the idea that anyting of value being produced is worth copying, I spent a few HOURS looking for something of simular shape that might you 3 bolts or pins, I found nothing like it but I did found crane blocks in meny shapes and sizes. I could immagine this thing being one side of a very large block but I'm not totally convenced. http://www.agd-equipment.co.uk/images/articles/small/100_t_hook_block_i.JPG