Scarred faceplate

[pratagy]

Hello!! This is my first thread. I'm from Brazil, and I've bought this used SP404 that a guy brought from Japan (it's impossible to find a new one here). When I got it a few months ago, the SP was a bit scarred, but now the marks has taken the entire faceplate. I was thinking if it is the high moisture we have here (amazon forest etc) and if some user had this same problem?
There's some way to clean the faceplate? The unit is functioning perfectly but... it looks like trash