I would expect there will be fuses at the other location in the mill to protect the supply cable to that busbar, and the thing pictured will just be an isolator. 160A will be the rating per phase of the isolator, just like a main switch in domestic CU has a current rating on it.
Of course I might be wrong
Can't you open it and have a look? I know it has a switch interlock, so if isolating that part of the installation is an issue, PM me. I might how to open it live.
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