[EC900]

Looks factory paint-over based on those coatings being slopped over.
Any ground was probably limited to the threaded inner portion of the welded in speed nut, grounding the bolt washer and terminal eyelets.
I’d carefully clean the inside threads with cotton swab of acetone, also clean off the bolt threads and terminal flat surfaces.
If your want, remove some paint of the flat of that speed nut too. It might be yellow zinc plated and rather than scratch it up and allow any rust, paint removal might be a better the first step.
Light buffing with #0000 rather than aggressive sand paper, touch up any bare metal.