I noticed the other day that 1 of the 4 covers on the 300J had curb rash. I have no idea how or when that happened, or if it's an old battle wound.
Curb rash can be the kiss of death for these; it doesn't just "buff out." So what's the big deal? It's a hubcap for cryin' out loud. No, it's not. Hubcaps are used on cop cars. This is a wheel cover specific to only 3 years of Letter Cars and they don't grow on trees.
It is worth the effort to work on the wound. On the right is the "before" photo. The rash is visible on the lower right. The photos below are the "after." I sanded with 180 grit and then 400. Then using the buff wheel I started with emory compound which didn't do a doggone thing. I spent the most time with the stainless compound on a spiral-sewn wheel. It removes the sanding scratches and minor abrasions but not the deep stuff. However, it improves appearance to the point that it is no longer noticeable except up close and under bright light. The last step is white rouge on a loose flannel wheel for the final buff and to bring up the shine to equal to or greater than the chrome center. This took about 2 hours of work. While it is not "fixed", it is noticeably better and this wheel cover has been saved.