I tried with that part number but didn't find it. I also tried PO 22300, thinking that was the most likely other reading of the number. That number shows up but is something else. So PO 2230C looks like a good read. I did find a few numbers close. For example, PO 2229 is a bracket for a knife weeder.
Unless somebody else finds the number, I guess it's a dead end on the brackets. I still think the basic unit is a Cub-F7 Tool Bar. I don't have a manual covering tool bars for the 100/140 tractors, so maybe it is for one of them. The Cub bar is 56 inches the one for the larger tractors is 78 inches.