The rusty face will clean-up with a brass wire brush and some hand-sanding.

If there are no broken-off threads in the screw holes these holes can be cleaned using a re-tapping tool(best) or a correct size screw.

Light rust in the voice-coil gap can be lightly honed with a piece of folded fine wet-or-dry emery paper.

Blown air to clean away the removed material.

Apply WD40, or similar, and let dry.

Check VC gap and clean with folded sticky tape.

You may be able to get the Tangerine Phase Plug off by levering it gently.