@ptss That plate is Permalloy. It has magnetic properties similar to Mu metal but is much less ductile. Mu metal can be formed easily into various shapes.
I have digital equipment all around analog gear and I don't have to shield anything. I do not have any interference or mystery noise. I spend my money on records and not trying to fix problems I do not have. The solution is not to buy equipment that is inadequately shielded.