Slave Leg Iron aka Fetter

I am a collector of items related to American slavery and have recently purchased a civil war era slave leg iron also known as a fetter. I found one in a museum that is identical to mine that was taken from an Underground Railroad house in Ohio in the civil war era. What makes mine so much more interesting is that it has carvings of patterns into the iron that were done by whoever was enslaved wearing these leg irons. I have never seen any slave iron with designs carved into it before. This makes the item much more interesting. I have attached the photos of mine as well as a photo of the ones in the museum giving a short history about them. I am curious if anyone else has seen this before and what they could possibly be worth. Thanks in advance!!