67-68 rear interior panel repair

The new panels look good in the pics plus you have the satisfaction knowing you DIY’d it.

I have this odd spot on my rear arm pad. Anyone had any luck cleaning if off or covering it up? No plans to replace anything. I’ve just been detailing all the interior pieces with mild soaps. Removing decades of dirt it seems. I have seen wear or spots like this on other pads and wonder how they form.
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