That plate is the CPC magnet assembly for adjusting DOT shape and
DOT centering. If your picture quality is good I would not move it. Check
a dot pattern image for roundness on the green CRT. If you need to
adjust it because the dot is not round, then straighten it so it is 90
degrees to the neck. Bear in mind, after CPC magnet adjustments, a
complete alignment and convergence may be necessary. Also, take care
to touch the tabs only. High voltages! keep away from bare terminals
and the HV wires.