What is this device? (8 photos)

Try to guess why you need this device?
I first thought it was a prosthesis.



 
Inspection photos to the end and read the answer.















This device came up with a prison guard by the name of John Gardner from the US state of Oregon May 22, 1866.
It was called the "Oregon shoe».
This device is attached to the leg instead of the classic prisoner's core chain, and its weight, which could vary between 3-12 kg, were selected individually and in accordance with the physique con.
This device was much more reliable and more progressive than the outdated moral metallic core with a chain.

Source: jane-baikal.livejournal.com