deaco, the actual P90s don't have any marking on the charging rails, so I would say your best bet is to go ahead and just remove it.
Since the "made in China" brand is raised lettering, but the area around it has been depressed (it's in a shallow area when compared to the rest of the charging rail), what I would do is fill it in with putty and then sand it.
If you use a soft automotive putty like Bondo you can smooth it out the lettering so the entire side of the charging rail is level, and then once it dries wet sand it with a 220 grit sandpaper. Wet sanding is where you either sand the piece under running water, or just regularly rinse off the sand paper during sanding (make sure the paper is marked that it can be used with wet sanding).
We're all new to the hobby at some point - welcome to the club

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